leetcode 59. Spiral Matrix II【蛇形填数】

Given a positive integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.

Example:

Input: 3
Output:
[
 [ 1, 2, 3 ],
 [ 8, 9, 4 ],
 [ 7, 6, 5 ]
]

就是leetcode 54Spiral Matrix【贪吃蛇】反回来而已

用上次第二种代码1A了

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> ans(n,vector<int>(n,0)); 
        int sx=0,sy=0,ex=n-1,ey=n-1;
        int tot=1;
        while(sx<=ex){
            for(int i=sy;i<=ey;i++)
                ans[sx][i]=tot++;
            for(int i=sx+1;i<=ex;i++)
                ans[i][ey]=tot++;
            for(int i=ey-1;i>=sy;i--)
                ans[ex][i]=tot++;
            for(int i=ex-1;i>=sx+1;i--)
                ans[i][sy]=tot++;
            sx++,sy++;
            ex--,ey--;
        }
        return ans;
    }
};