【LeetCode】59. Spiral Matrix II

题目描述

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 ]
]

解题思路

和【LeetCode】54. Spiral Matrix 思路一样。只是此次需要一个全局的计数器，每次往矩阵中写入当前计数值并增加计数器即可。

AC代码

class Solution {
public:
vector<vector<int>> generateMatrix(int n) {
vector<vector<int>> ans;
for (int i = 0; i < n; ++i) {
vector<int> temp(n, 0);
ans.push_back(temp);
}
vector<vector<int>> dirs = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
int nSteps[2] = {n, n -1};
int curDir = 0;
int curRow = 0, curCol = -1;
int totalCnt = 1;
int cnt = 0;
while (nSteps[curDir % 2]) {
curRow += dirs[curDir][0];
curCol += dirs[curDir][1];
ans[curRow][curCol] = totalCnt;
totalCnt++;
cnt++;
if (cnt == nSteps[curDir % 2]) {
cnt = 0;
nSteps[curDir % 2]--;
curDir = (curDir + 1) % 4;
}
}

return ans;
}
};