Add solution for leetcode's surround-region

Author: pulkitent

src/main/java/com/pulkit/datastructures_algorithms/done/graphs/SurroundedRegions.java

@@ -0,0 +1,130 @@
+import java.util.HashSet;
+import java.util.Set;
+
+
+/*
+input
+[   ['O','O','O','O','X','X'],
+    ['O','O','O','O','O','O'],
+    ['O','X','O','X','O','O'],
+    ['O','X','O','O','X','O'],
+    ['O','X','O','X','O','O'],
+    ['O','X','O','O','O','O']
+]
+
+
+mine output
+[   ['O','O','O','O','X','X'],
+    ['O','O','O','O','O','O'],
+    ['O','X','X','X','X','O'],
+    ['O','X','X','X','X','O'],
+    ['O','X','X','X','X','O'],
+    ['O','X','O','O','O','O']
+]
+
+expected
+[   ['O','O','O','O','X','X'],
+    ['O','O','O','O','O','O'],
+    ['O','X','O','X','O','O'],
+    ['O','X','O','O','X','O'],
+    ['O','X','O','X','O','O'],
+    ['O','X','O','O','O','O']
+]
+ */
+
+
+class Solution {
+    public static void main(String[] s) {
+        char board[][] = {{'O', 'O', 'O', 'O', 'X', 'X'},
+                {'O', 'O', 'O', 'O', 'O', 'O'},
+                {'O', 'X', 'O', 'X', 'O', 'O'},
+                {'O', 'X', 'O', 'O', 'X', 'O'},
+                {'O', 'X', 'O', 'X', 'O', 'O'},
+                {'O', 'X', 'O', 'O', 'O', 'O'}};
+
+        for (int i = 0; i < board.length; i++) {
+            for (int j = 0; j < board[0].length; j++) {
+                if (i == 0 || i == (board.length - 1) || j == 0 || j == (board[0].length - 1)) {
+                    if (board[i][j] == 'O') {
+                        makeBoundaryZerosToOne(board, i, j, new HashSet<>(), new HashSet<>());
+                    }
+                }
+            }
+        }
+
+        for (int i = 0; i < board.length; i++) {
+            for (int j = 0; j < board[0].length; j++) {
+                if (board[i][j] == 'O') {
+                    board[i][j] = 'X';
+                }
+            }
+        }
+
+        for (int i = 0; i < board.length; i++) {
+            for (int j = 0; j < board[0].length; j++) {
+                if (board[i][j] == '1') {
+                    board[i][j] = 'O';
+                }
+            }
+        }
+
+        for (int i = 0; i < board.length; i++) {
+            for (int j = 0; j < board[0].length; j++) {
+                System.out.print(board[i][j]+" ");
+            }
+            System.out.println("");
+        }
+    }
+
+    private static void makeBoundaryZerosToOne(char[][] board, int i, int j,
+                                               Set<Integer> visitedI, Set<Integer> visitedJ) {
+        if (i == 2 && j == 2) {
+            System.out.println("debug");
+        }
+
+        if (isNotInRange(board, i, j))
+            return;
+
+        if (visitedI.contains((i+1) * 100000) && visitedJ.contains(j))
+            return;
+
+        board[i][j] = '1';
+        visitedI.add((i+1) * 100000);
+        visitedJ.add(j);
+
+        if (!isNotInRange(board, i + 1, j) && board[i + 1][j] == 'O') {
+            makeBoundaryZerosToOne(board, i + 1, j, visitedI, visitedJ);
+        }
+        if (!isNotInRange(board, i, j + 1) && board[i][j + 1] == 'O') {
+            makeBoundaryZerosToOne(board, i, j + 1, visitedI, visitedJ);
+        }
+        if (!isNotInRange(board, i, j - 1) && board[i][j - 1] == 'O') {
+            makeBoundaryZerosToOne(board, i, j - 1, visitedI, visitedJ);
+        }
+        if (!isNotInRange(board, i - 1, j) && board[i - 1][j] == 'O') {
+            makeBoundaryZerosToOne(board, i - 1, j, visitedI, visitedJ);
+        }
+    }
+
+    private static boolean isNotInRange(char[][] board, int i, int j) {
+        return i < 0 || j < 0 || i >= board.length || j >= board[0].length;
+    }
+
+    private class cell {
+        private int i;
+        private int j;
+
+        public cell(int i, int j) {
+            this.i = i;
+            this.j = j;
+        }
+
+        public int getI() {
+            return i;
+        }
+
+        public int getJ() {
+            return j;
+        }
+    }
+}