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leetcode
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‎PossibleBipartition/possible_bipartition.dart

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/*
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-* 886. Possible Bipartition *-
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We want to split a group of n people (labeled from 1 to n) into two groups of any size. Each person may dislike some other people, and they should not go into the same group.
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Given the integer n and the array dislikes where dislikes[i] = [ai, bi] indicates that the person labeled ai does not like the person labeled bi, return true if it is possible to split everyone into two groups in this way.
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Example 1:
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Input: n = 4, dislikes = [[1,2],[1,3],[2,4]]
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Output: true
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Explanation: group1 [1,4] and group2 [2,3].
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Example 2:
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Input: n = 3, dislikes = [[1,2],[1,3],[2,3]]
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Output: false
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Example 3:
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Input: n = 5, dislikes = [[1,2],[2,3],[3,4],[4,5],[1,5]]
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Output: false
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Constraints:
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1 <= n <= 2000
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0 <= dislikes.length <= 104
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dislikes[i].length == 2
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1 <= dislikes[i][j] <= n
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ai < bi
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All the pairs of dislikes are unique.
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*/
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import 'dart:collection';
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class A {
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bool possibleBipartition(int n, List<List<int>> dislikes) {
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List<List<int>> graph =
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List.filled(n, 0).map((e) => List.filled(n, 0)).toList();
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for (List<int> d in dislikes) {
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graph[d[0] - 1][d[1] - 1] = 1;
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graph[d[1] - 1][d[0] - 1] = 1;
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}
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List<int> group = List.filled(n, 0);
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for (int i = 0; i < n; i++) {
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if (group[i] == 0 && !depthFirstSearch(graph, group, i, 1)) {
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return false;
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}
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}
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return true;
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}
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bool depthFirstSearch(
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List<List<int>> graph, List<int> group, int index, int g) {
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group[index] = g;
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for (int i = 0; i < graph.length; i++) {
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if (graph[index][i] == 1) {
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if (group[i] == g) {
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return false;
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}
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if (group[i] == 0 && !depthFirstSearch(graph, group, i, -g)) {
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return false;
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}
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}
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}
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return true;
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}
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}
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// breadth first Search
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class B {
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bool possibleBipartition(int n, List<List<int>> dislikes) {
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int len = dislikes.length;
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if (len < 2) return true;
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List<int> color = List.filled(n + 1, 0);
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List<List<int>> graph = [];
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for (int i = 0; i <= n; i++) {
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List<int> tmp = [];
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graph.add(tmp);
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}
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for (int i = 0; i < len; i++) {
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int m = dislikes[i][0];
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int n = dislikes[i][1];
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graph[m].add(n);
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graph[n].add(m);
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}
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for (int i = 1; i <= n; i++) {
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if (color[i] == 0) {
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color[i] = 1;
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Queue<int> q = Queue();
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q.add(i);
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while (q.isNotEmpty) {
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int cur = q.removeFirst();
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for (int j in graph[cur]) {
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if (color[j] == 0) {
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color[j] = color[cur] == 1 ? 2 : 1;
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q.add(j);
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} else {
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if (color[j] == color[cur]) return false;
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}
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}
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}
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}
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}
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return true;
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}
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}
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class C {
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HashMap<int, List<int>> map = HashMap();
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bool possibleBipartition(int n, List<List<int>> dislikes) {
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for (List<int> dis in dislikes) {
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if (map[dis[0]] == null) map[dis[0]] = [];
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map[dis[0]]?.add(dis[1]);
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if (map[dis[1]] == null) map[dis[1]] = [];
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map[dis[1]]?.add(dis[0]);
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}
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List<int> colors = List.filled(n + 1, 0);
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for (int i = 1; i <= n; i++) {
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if (map[i] == null) continue;
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if (colors[i] == 0 && !helper(i, colors, 1)) return false;
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}
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return true;
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}
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bool helper(int index, List<int> colors, int color) {
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if (colors[index] != 0) return color == colors[index];
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int len = map[index]!.length;
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colors[index] = color;
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for (int i = 0; i < len; i++) {
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if (!helper(map[index]![i], colors, -1 * color)) return false;
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}
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return true;
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}
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}

‎PossibleBipartition/possible_bipartition.go

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package main
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func possibleBipartition(n int, dislikes [][]int) bool {
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var graph = make([][]int, n)
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for _, pair := range dislikes {
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i := pair[0] - 1
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j := pair[1] - 1
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graph[i] = append(graph[i], j)
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graph[j] = append(graph[j], i)
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}
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var colors = make([]int, n)
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for i := 0; i < n; i++ {
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if colors[i] == 0 && !isValid(&graph, &colors, i, 1) {
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return false
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}
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}
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return true
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}
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func isValid(graph *[][]int, colors *[]int, i int, color int) bool {
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if (*colors)[i] != 0 {
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return (*colors)[i] == color
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}
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(*colors)[i] = color
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for _, j := range (*graph)[i] {
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if (*colors)[i] == (*colors)[j] || !isValid(graph, colors, j, -color) {
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return false
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}
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}
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return true
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}

‎PossibleBipartition/possible_bipartition.md

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# 🔥 Possible Bipartition 🔥 || 3 Approaches || Simple Fast and Easy || with Explanation
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## Solution - 1 Depth First Search
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```dart
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class Solution {
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bool possibleBipartition(int n, List<List<int>> dislikes) {
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List<List<int>> graph =
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List.filled(n, 0).map((e) => List.filled(n, 0)).toList();
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for (List<int> d in dislikes) {
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graph[d[0] - 1][d[1] - 1] = 1;
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graph[d[1] - 1][d[0] - 1] = 1;
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}
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List<int> group = List.filled(n, 0);
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for (int i = 0; i < n; i++) {
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if (group[i] == 0 && !depthFirstSearch(graph, group, i, 1)) {
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return false;
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}
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}
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return true;
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}
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bool depthFirstSearch(
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List<List<int>> graph, List<int> group, int index, int g) {
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group[index] = g;
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for (int i = 0; i < graph.length; i++) {
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if (graph[index][i] == 1) {
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if (group[i] == g) {
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return false;
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}
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if (group[i] == 0 && !depthFirstSearch(graph, group, i, -g)) {
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return false;
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}
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}
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}
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return true;
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}
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}
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```
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## Solution - 2 Breadth First Search
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```dart
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import 'dart:collection';
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class Solution {
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bool possibleBipartition(int n, List<List<int>> dislikes) {
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int len = dislikes.length;
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if (len < 2) return true;
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List<int> color = List.filled(n + 1, 0);
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List<List<int>> graph = [];
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for (int i = 0; i <= n; i++) {
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List<int> tmp = [];
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graph.add(tmp);
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}
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for (int i = 0; i < len; i++) {
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int m = dislikes[i][0];
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int n = dislikes[i][1];
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graph[m].add(n);
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graph[n].add(m);
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}
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for (int i = 1; i <= n; i++) {
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if (color[i] == 0) {
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color[i] = 1;
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Queue<int> q = Queue();
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q.add(i);
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while (q.isNotEmpty) {
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int cur = q.removeFirst();
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for (int j in graph[cur]) {
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if (color[j] == 0) {
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color[j] = color[cur] == 1 ? 2 : 1;
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q.add(j);
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} else {
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if (color[j] == color[cur]) return false;
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}
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}
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}
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}
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}
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return true;
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}
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}
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```
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## Solution - 3 Memoization
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```dart
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import 'dart:collection';
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class Solution {
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HashMap<int, List<int>> map = HashMap();
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bool possibleBipartition(int n, List<List<int>> dislikes) {
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for (List<int> dis in dislikes) {
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if (map[dis[0]] == null) map[dis[0]] = [];
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map[dis[0]]?.add(dis[1]);
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if (map[dis[1]] == null) map[dis[1]] = [];
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map[dis[1]]?.add(dis[0]);
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}
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List<int> colors = List.filled(n + 1, 0);
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for (int i = 1; i <= n; i++) {
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if (map[i] == null) continue;
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if (colors[i] == 0 && !helper(i, colors, 1)) return false;
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}
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return true;
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}
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bool helper(int index, List<int> colors, int color) {
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if (colors[index] != 0) return color == colors[index];
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int len = map[index]!.length;
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colors[index] = color;
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for (int i = 0; i < len; i++) {
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if (!helper(map[index]![i], colors, -1 * color)) return false;
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}
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return true;
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}
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}
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```

‎README.md

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- [**739.** Daily Temperatures](DailyTemperatures/daily_temperatures.dart)
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- [**1971.* Find if Path Exists in Graph](FindIfPathExistsInGraph/find_if_path_exists_in_graph.dart)
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- [**841.** Keys and Rooms](KeysAndRooms/keys_and_rooms.dart)
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- [**886.** Possible Bipartition](PossibleBipartition/possible_bipartition.dart)
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## Reach me via
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