LeetCode-48. Rotate Image

LeetCode-48. Rotate Image

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Note:

You have to rotate the image ​​in-place​​, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

Example 1:

Given input matrix = [ [1,2,3], [4,5,6], [7,8,9]],rotate the input matrix in-place such that it becomes:[ [7,4,1], [8,5,2], [9,6,3]]

Example 2:

Given input matrix =[ [ 5, 1, 9,11], [ 2, 4, 8,10], [13, 3, 6, 7], [15,14,12,16]], rotate the input matrix in-place such that it becomes:[ [15,13, 2, 5], [14, 3, 4, 1], [12, 6, 8, 9], [16, 7,10,11]]

题解：

先对角线交换，再左右交换即可

class Solution {public: void swap(int &a, int &b) { int idx = a; a = b; b = idx; } void rotate(vector>& matrix) { int n = matrix.size(); if (n <= 1) { return; } for (int i = 0; i < n; i++) { for (int j = i; j < n; j++) { swap(matrix[i][j], matrix[j][i]); } } for (int i = 0; i < n; i++) { for (int j = 0; j < n / 2; j++) { swap(matrix[i][j], matrix[i][n - j - 1]); } } }};

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