2

Author: kedebug

WordSearch/WordSearch.cpp

@@ -0,0 +1,68 @@
+class Solution {
+public:
+    bool exist(vector<vector<char>>& board, string word) {
+        // Start typing your C/C++ solution below
+        // DO NOT write int main() function
+        
+        this->word = word;
+        row = board.size();
+        if (row == 0) return false;
+        col = board[0].size();
+        
+        for (int i = 0; i < row; i++) {
+            for (int j = 0; j < col; j++) {
+                map[i][j] = board[i][j];
+                visited[i][j] = false;
+            }
+        }
+        bool flag = false;
+        for (int i = 0; i < row; i++) {
+            for (int j = 0; j < col; j++) {
+                if (map[i][j] == word[0]) {
+                    visited[i][j] = true;
+                    flag = DFS(i, j, 1);
+                    visited[i][j] = false;
+                    if (flag) return flag;
+                }
+            }
+        }
+        return false;
+    }
+    
+private:
+    bool isValid(int x, int y) {
+        if (0 <= x && x < row && 0 <= y && y < col) {
+            return true;
+        }
+        return false;
+    }
+    
+    bool DFS(int x, int y, int p) {
+        if (p == word.size()) 
+            return true;
+        
+        bool flag = true;
+        for (int i = 0; i < 4; i++) {
+            int a = x + dx[i];
+            int b = y + dy[i];
+            if (isValid(a, b) && !visited[a][b] && map[a][b] == word[p]) {
+                visited[a][b] = true;
+                flag = DFS(a, b, p + 1);
+                visited[a][b] = false;
+                if (flag) return true;
+            }
+        }
+        return false;
+    }
+
+private:
+    static const int MAXN = 1010;
+    int dx[4] = {1, -1, 0, 0};
+    int dy[4] = {0, 0, -1, 1};
+    int row, col;
+    // 56ms judge large
+    // much faster than pass-by-reference
+    char map[MAXN][MAXN];
+    bool visited[MAXN][MAXN];
+    string word;
+};