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 ]
]

 分析： 典型的题目 注意二维数组遍历的方式，“一圈圈”来遍历比较直接

class Solution {
public:
    vector<vector<int>> generateMatrix(int n) {
        vector<vector<int>> matrix(n, vector<int>(n,0));
        int len;
        int cnt=1;
        int x=0,y=0;
       
        for(int i=0; i*2<n; i++){
            cout << "i = "<< i<<endl;
            // start point (i,i)
            len = n-i*2;
            x = y =i;
            if(len == 1)
                matrix[x][y] =cnt;
            // go right
            for(int j=0; j<len-1; j++){
                matrix[x][y++] = cnt;
                cnt++;
            }
            
            // go down
            for(int j=0; j<len-1; j++){
                matrix[x++][y] = cnt;
                cnt++;
            }
            
            // go left
            for(int j=0; j<len-1; j++){
                matrix[x][y--] = cnt;
                cnt++;
            }
            
            // go up
            for(int j=0; j<len-1; j++){
                matrix[x--][y] = cnt;
                cnt++;
            }
        }
        return matrix;
    }
};

PS: 寒假开始， 每日重点就是leetcode， 两个星期看看能做多少