[LeetCode OJ]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 ]]

没什么算法可言，模拟数据写入顺序依次写入即可

AC Code:

class Solution {public:    vector<vector<int>> generateMatrix(int n) {        vector<vector<int>> rst(n, vector<int>(n , -1));        int num = 1;        int i = 0;        int j = 0;        int pi,pj;        int p = 0;//0: right , 1: down, 2: left, 3: up        if(n == 0)            return vector<vector<int>>();        rst[0][0] = 1;        while(num < n*n)        {            switch(p)            {                case 0:                    pi = i;                    pj = j+1;                    break;                case 1:                    pi = i+1;                    pj = j;                    break;                case 2:                    pi = i;                    pj = j-1;                    break;                case 3:                    pi = i-1;                    pj = j;                    break;                default:                    break;            }                        if(pi<0 || pj<0 || pi>=n || pj>= n)            {                p = (++p)%4;            }            else if(rst[pi][pj] != -1)            {                p = (++p)%4;            }            else            {                i = pi;                j = pj;                num++;                rst[i][j] = num;            }        }                return rst;    }};