Given an integer n, generate a square matrix filled with elements from 1 to n 2 in spiral order.
For example,
Given n =3,
You should return the following matrix:
[ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ]
注意左->右可遍历全，剩余两个方向遍历时需+1，最后一个方向掐头去尾避免重复遍历
class Solution { public: vector<vector<int> > generateMatrix(int n) { vector<vector<int>> result(n,vector<int>(n)); if(n==0) return result; int step = 1; int left = 0; int right = n-1; int top = 0; int bottom = n-1; while(left<=right && top<=bottom) { // 左->右 for(int i=left;i<=right;i++) { result[top][i] = step; step++; } //上->下 for(int i=top+1;i<=bottom;i++) { result[i][right] = step; step++; } //右->左 for(int i=right-1;i>=left;i--) { result[bottom][i] = step; step++; } //下->上 for(int i=bottom-1;i>top;i--) { result[i][left] = step; step++; } left++; right--; top++; bottom--; } return result; } };