Given a positive integer n, generate a square matrix filled with elements from 1 to n2 in spiral order.
Example:
Input: 3 Output: [ [ 1, 2, 3 ], [ 8, 9, 4 ], [ 7, 6, 5 ] ]
AC code:
class Solution {
public:
vector<vector<int>> generateMatrix(int n) {
vector<vector<int>> ans(n, vector<int>(n, 0));
int top = 0, bottom = n-1;
int left = 0, right = n-1;
int num = 1;
while (top <= bottom && left <= right) {
// left -> right
for (int i = left; i <= right; ++i) {
ans[top][i] = num++;
}
top++;
// top -> bottom
for (int i = top; i <= bottom; ++i) {
ans[i][right] = num++;
}
right--;
// right -> left
for (int i = right; i >= left; --i) {
ans[bottom][i] = num++;
}
bottom--;
// bottom -> top
for (int i = bottom; i >= top; --i) {
ans[i][left] = num++;
}
left++;
}
return ans;
}
};
原文：https://www.cnblogs.com/ruruozhenhao/p/9818801.html