LeetCode 59. Spiral Matrix II

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

For example,
Given n = 3,

You should return the following matrix:

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

蛇形填数，之前有一道类似的题。

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>>ans(n, vector<int>(n));

        int x = 0, y = 0, res = 0;
        while(true)
        {
            for(int i=y; i<n-y; ++ i)
                ans[x][i] = ++ res;
            
            if(2*x + 1 >= n)
                break;

            for(int i=x+1; i<n-x; ++ i)
                ans[i][n-y-1] = ++ res;

            if(2*y + 1 >= n)
                break;

            for(int i=n-y-2; i >= y; -- i)
                ans[n-x-1][i] = ++ res;

            if(2*x + 2 == n)
                break;

            for(int i=n-x-2; i > x; -- i)
                ans[i][y] = ++ res;

            if(2*y + 2 == n)
                break;

            x ++, y ++;
        }
        return ans;
    }
};