59. Spiral Matrix II(螺旋矩阵 II)解法(C++ & 注释)
2020-07-14 05:29
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59. Spiral Matrix II(螺旋矩阵 II)
1. 题目描述
给定一个正整数 n,生成一个包含 1 到 n2 所有元素,且元素按顺时针顺序螺旋排列的正方形矩阵。
示例:
输入: 3
输出:
[
[ 1, 2, 3 ],
[ 8, 9, 4 ],
[ 7, 6, 5 ]
]
2. 按层遍历(Layer-by-Layer)
2.1 解题思路
这题基本算是54. 螺旋矩阵的简单版,思路几乎都是一样,只是本题简单了不少,只需考虑正方形的情况。所以大家可以参考一下前一题的思路,再瞅瞅下面的代码,应该就木有问题的啦~~~~
2.2 实例代码
class Solution { public: vector<vector<int>> generateMatrix(int n) { int layers = n / 2, num = 1; vector<vector<int>> ans(n, vector<int>(n, 0)); if (!n) return ans; for (int k = 0; k <= layers; k++) { int i = k, j = k, alls = n - i == 1 ? 1 : 4 * (n - i) - 4; while (j < n) { ans[i][j] = num++; j++; alls--; } j--; i++; while (alls > 0 && i < n) { ans[i][j] = num++; i++; alls--; } i--; j--; while (alls > 0 && j >= k) { ans[i][j] = num++; j--; alls--; } j++; i--; while (alls > 0 && i > k) { ans[i][j] = num++; i--; } n--; } return ans; } };
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