回溯法 exist

Author: “gitgou”

exist.cpp

@@ -0,0 +1,41 @@
+#include<iostream>
+#include<vector>
+#include<algorithm>
+#include<string>
+using namespace std;
+
+    bool back(vector<vector<char>>& board, string word, vector<vector<bool>>& hash, int row, int col){
+        if(word.size() == 0)
+            return true;
+        if(row < 0 || row >= board.size() || col < 0 || col >= board[0].size())
+            return false;
+        if(hash[row][col] == true)
+            return false;
+        if(board[row][col] != word[0])
+            return false;
+
+        hash[row][col] = 1;
+        word = word.substr(1);
+        if(back(board, word, hash, row - 1, col) == false && 
+                back(board, word, hash, row + 1, col) &&
+                back(board, word, hash, row , col - 1) &&
+                back(board, word, hash, row , col + 1)){
+                    hash[row][col] = false;
+                    return false;
+                }
+                
+        return true;
+    }
+
+    bool exist(vector<vector<char>>& board, string word) {
+        vector<vector<bool> > hash(board.size(), vector<bool>(board[0].size(), false));
+        for(int i = 0; i < board.size(); ++i){
+            for(int j = 0; j < board[0].size(); ++j){
+                if(back(board, word, hash, i, j)){
+                    return true;
+                }
+            }
+        }
+        return false;
+
+    }