Spiral matrix II <leetcode>

Given an integerN, Generate a square matrix filled with elements from 1N2 in spiral order.

For example,
GivenN=3,

You shoshould return the following matrix:

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

]
Algorithm: the algorithm is divided into four directions, with scanning in the upper right and lower left. If you can enter a number, you can change the direction. This question is not difficult, but it is prone to small errors. The Code is as follows:

 1 class Solution { 2 public: 3     vector<vector<int>> result; 4     vector<vector<int> > generateMatrix(int n) { 5         int total=n*n; 6         int x=0; 7         int y=0; 8         int direction=0; 9         result.clear();10         for(int i=0;i<n;i++)11         {12             vector<int> nn;13             result.push_back(nn);14             for(int j=0;j<n;j++)15             {16                 result[i].push_back(0);17             }18         }19         for(int i=1;i<=total;i++)20         {21             if(0==result[x][y])22             {23                 result[x][y]=i;24             }25             else if(0==direction)26             {27                 if(y+1<=n-1&&0==result[x][y+1])28                 {29                   result[x][y+1]=i;30                   y++;31                 }32                 else 33                 {34                     direction=1;35                 36                     i--;37                 }38             }39             else if(1==direction)40             {41                 if(x+1<=n-1&&0==result[x+1][y])42                 {43                    result[x+1][y]=i;44                    x++;45                 }46                 else47                 {48                     direction=2;49                     i--;50                 }51             }52             else if(2==direction)53             {54                 if(y-1>=0&&0==result[x][y-1])55                 {56                     result[x][y-1]=i;57                     y--;58                 }59                 else60                 {61                     direction=3;62                     i--;63                 }64             }65             else if(3==direction)66             {67                 if(x-1>=0&&0==result[x-1][y])68                 {69                     result[x-1][y]=i;70                     x--;71                 }72                 else73                 {74                     direction=0;75                     i--;76                 }77             }78         }79         return result;80     }81 };

 

Spiral matrix II <leetcode>