1. 개요

2. 투쟁

3. 코드

int numIslands(vector<vector<char>>& grid) {

        if(grid.size() == 0) return 0;

        int count = 0;
        for (int i = 0; i < grid.size(); i++){
            for (int j = 0; j < grid[0].size(); j++){
                if(grid[i][j] == '0') {
                    continue;
                } else {
                    BFS(grid, i, j, count);
                }
            }
        }
        return count;
    }

void BFS(vector<vector<char>>& grid, int i, int j, int& count){
        vector<vector<int>> dir = {{-1,0}, {1,0}, {0,-1}, {0,1}};
        queue<vector<int>> q;
        vector<int> start = {i, j};
        q.push(start);
        while(!q.empty()){
            vector<int> curr = q.front();
            grid[curr[0]][curr[1]] = '0'; 
            q.pop();
            for (auto v:dir){
                int newCol = curr[0] + v[0];
                int newRow = curr[1] + v[1];
                if (newCol < 0 || newRow < 0 || newCol >= grid.size() || newRow >= grid[0].size() || grid[newCol][newRow] == '0'){
                    continue;
                } else {
                    vector<int> nextPos = {newCol, newRow};
                    q.push(nextPos);
                }
            }
        }
        count++;
    }

static void BFS(vector<vector<char>>& grid, int i, int j, int& count){
        vector<vector<int>> dir = {{-1,0}, {1,0}, {0,-1}, {0,1}};
        queue<vector<int>> q;
        vector<int> start = {i, j};
        q.push(start); 
        while(!q.empty()){
            vector<int> curr = q.front();
            q.pop();
            grid[curr[0]][curr[1]] = '0'; 
            for (auto v:dir){
                int newCol = curr[0] + v[0];
                int newRow = curr[1] + v[1];
                if (newCol < 0 || newRow < 0 || newCol >= grid.size() || newRow >= grid[0].size() || grid[newCol][newRow] == '0'){
                    continue;
                } else {
                    vector<int> nextPos = {newCol, newRow};
                    grid[curr[0]][curr[1]] = '0'; // <= Solution                  
                    q.push(nextPos);
                }
            }
        }
        count++;
    }

4. 설명