Add 130_Surrounded_Regions.cpp

C++/130_Surrounded_Regions.cpp

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+//130. Surrounded Regions
+/*
+Given a 2D board containing 'X' and 'O', capture all regions surrounded by 'X'.
+
+A region is captured by flipping all 'O's into 'X's in that surrounded region.
+
+For example,
+X X X X
+X O O X
+X X O X
+X O X X
+After running your function, the board should be:
+
+X X X X
+X X X X
+X X X X
+X O X X
+
+Tag: Breadth-first Search, Union Find
+
+Author: Xinyu Liu
+*/
+#include <vector>
+using namespace std;
+
+class Solution {
+public:
+    void solve(vector<vector<char>>& board) {
+        int i,j;
+        int row = board.size();
+        if(!row)
+            return;
+        int col = board[0].size();
+
+        for(i = 0; i < row; i++){
+            nearcheck(board, i, 0, row,col);
+            if(col > 1)
+                nearcheck(board, i, col - 1, row, col);
+        }
+        for(j = 1; j + 1 < col; j++){
+            nearcheck(board, 0, j, row, col);
+            if(row > 1)
+                nearcheck(board, row - 1, j, row, col);
+        }
+        for(i = 0; i < row; i++)
+            for(j = 0; j < col; j++)
+                if(board[i][j] == 'O')
+                    board[i][j] = 'X';
+        for(i = 0; i < row; i++)
+            for(j = 0; j < col; j++)
+                if(board[i][j] == '1')
+                    board[i][j] = 'O';
+    }
+    void nearcheck(vector<vector<char> >&vec, int i, int j, int row, int col){
+        if(vec[i][j] == 'O'){
+            vec[i][j] = '1';
+            if(i > 1)
+                nearcheck(vec, i - 1, j, row, col);
+            if(j > 1)
+                nearcheck(vec, i, j - 1, row, col);
+            if(i < row - 1)
+                nearcheck(vec, i + 1, j, row, col);
+            if(j < col - 1)
+                nearcheck(vec, i, j + 1, row, col);
+        }
+    }
+};
+
+void main(){
+    char c0[] = {'X','X','X','X'};
+    vector<char> v0 (begin(c0), end(c0));
+    char c1[] = {'X','O','O','X'};
+    vector<char> v1 (begin(c1), end(c1));
+    char c2[] = {'X','X','O','X'};
+    vector<char> v2 (begin(c2), end(c2));
+    char c3[] = {'X','X','X','X'};
+    vector<char> v3 (begin(c3), end(c3));
+    vector<vector<char>> v;
+    v.push_back(v0);
+    v.push_back(v1);
+    v.push_back(v2);
+    v.push_back(v3);
+    Solution sol;
+    sol.solve(v);
+}