【数据结构与算法】（十一）图

邻接矩阵

邻接表

广度优先搜索（BFS） queue visited prev

深度优先搜索（DFS）回溯算法

LeetCode

1 岛屿数量

public:
    int row,columns;
    int numIslands(vector<vector<char>>& grid) {
        
        row=grid.size();
        int count=0;
        if(row==0) return count;
        columns=grid[0].size();
        
        for(int i=0;i<row;i++){
            for(int j=0;j<columns;j++){
                if(grid[i][j]=='1'){
                    count++;
                    dfs(grid,i,j);
                }
            }
        }
        return count;
    }
    
    void dfs(vector<vector<char>>& grid,int r,int c){
        grid[r][c] = '0';
        if(r-1>=0&&grid[r-1][c]=='1') dfs(grid,r-1,c);
        if(c+1<columns&&grid[r][c+1]=='1') dfs(grid,r,c+1);
        if(c-1>=0&&grid[r][c-1]=='1') dfs(grid,r,c-1);
        if(r+1<row&&grid[r+1][c]=='1') dfs(grid,r+1,c);
    }