6.3—矩阵

1. 岛屿的周长

class Solution {
public:
    int islandPerimeter(vector<vector<int>>& grid) {
        int ans=0;
        //遍历
        int row = grid.size();
        int col = grid[0].size();
        for(int i=0;i<row;i++){
            for(int j=0;j<col;j++){
                if(grid[i][j]==1){
                    if(i==0){
                        ans++;
                    }
                    if(j==0){
                        ans++;
                    }
                    if(i==row-1){
                        ans++;
                    }
                    if(j==col-1){
                        ans++;
                    }
                    if(i-1>=0){
                        if(grid[i-1][j]==0){
                            ans++;
                        }
                    }
                    if(i+1<row){
                        if(grid[i+1][j]==0){
                            ans++;
                        }
                    }
                    if(j-1>=0){
                        if(grid[i][j-1]==0){
                            ans++;
                        }
                    }
                    if(j+1<col){
                        if(grid[i][j+1]==0){
                            ans++;
                        }
                    }
                }
            }
        }
        return ans;                                        
    }
};

矩阵，m*n