LeetCode-130-Surrounded Regions

Posted 无名路人甲

tags:

篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了LeetCode-130-Surrounded Regions相关的知识,希望对你有一定的参考价值。

算法描述:

Given a 2D board containing ‘X‘ and ‘O‘ (the letter O), capture all regions surrounded by ‘X‘.

A region is captured by flipping all ‘O‘s into ‘X‘s in that surrounded region.

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

Explanation:

Surrounded regions shouldn’t be on the border, which means that any ‘O‘ on the border of the board are not flipped to ‘X‘. Any ‘O‘ that is not on the border and it is not connected to an ‘O‘ on the border will be flipped to ‘X‘. Two cells are connected if they are adjacent cells connected horizontally or vertically.

解题思路:深度优先搜索或者广度优先搜索。从边界开始搜索,将符合条件的值得索引放入队列中,并用额外的矩阵标记访符合要求的数值位置。

 void solve(vector<vector<char>>& board) {
        int m = board.size();
        if(m==0) return;
        int n = board[0].size();
        if(n==0) return;
        
        vector<vector<int>> alive(m, vector<int>(n, 0));
        queue<pair<int, int>> que;
        for(int i=0; i< m; i++){
            if(board[i][0] == O){
                alive[i][0] =1;
                que.push(make_pair(i,0));
            }
            if(board[i][n-1] == O){
                alive[i][n-1] =1;
                que.push(make_pair(i,n-1));
            }
        }
        
         for(int i=0; i< n; i++){
            if(board[0][i] == O){
                alive[0][i] =1;
                que.push(make_pair(0,i));
            }
            if(board[m-1][i] == O){
                alive[m-1][i] =1;
                que.push(make_pair(m-1,i));
            }
        }
        
        while(!que.empty()){
            pair<int,int> temp = que.front();
            que.pop();
            int dx[] = {-1,0,1,0};
            int dy[] = {0,1,0,-1};
            for(int i = 0; i < 4; i++){
                int ax = temp.first + dx[i];
                int ay = temp.second + dy[i];
                if(ax >= 0 && ay >=0 && ax < m && ay < n && alive[ax][ay] ==0 && board[ax][ay] == O){
                    alive[ax][ay] = 1;
                    que.push(make_pair(ax,ay));
                }
            }
        }
        for(int i=0; i < m; i++){
            for(int j=0; j <n; j++){
                if(alive[i][j]==0 && board[i][j]==O)
                    board[i][j] =X;
            }
        }
    }

 

以上是关于LeetCode-130-Surrounded Regions的主要内容,如果未能解决你的问题,请参考以下文章

LeetCode(130) Surrounded Regions

LeetCode-130-Surrounded Regions

[LeetCode]130 Surrounded Regions(DFS)

leetcode 130. Surrounded Regions----- java

[LeetCode] 130. Surrounded Regions

一天一道LeetCode#130. Surrounded Regions