65 lines
1.3 KiB
Markdown
65 lines
1.3 KiB
Markdown
# 旋转图像
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## 题目
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给定一个 n × n 的二维矩阵 matrix 表示一个图像。请你将图像顺时针旋转 90 度。
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你必须在 原地 旋转图像，这意味着你需要直接修改输入的二维矩阵。请不要 使用另一个矩阵来旋转图像。
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示例 1：
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输入：matrix = [[1,2,3],[4,5,6],[7,8,9]]
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输出：[[7,4,1],[8,5,2],[9,6,3]]
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示例 2：
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输入：matrix = [[5,1,9,11],[2,4,8,10],[13,3,6,7],[15,14,12,16]]
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输出：[[15,13,2,5],[14,3,4,1],[12,6,8,9],[16,7,10,11]]
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提示：
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n == matrix.length == matrix[i].length
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1 <= n <= 20
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-1000 <= matrix[i][j] <= 1000
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## 思路
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- 观察特点
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- 对角线交换
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- 左右镜像交换
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## 代码
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```java
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class Solution {
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public void rotate(int[][] matrix) {
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// Init: n(length)
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int n = matrix.length;
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// Traverse 1
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for (int i = 0; i < n; i++) {
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for (int j = i; j < n; j++) {
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int tmp = matrix[i][j];
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matrix[i][j] = matrix[j][i];
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matrix[j][i] = tmp;
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}
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}
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// Traverse 2
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for (int i = 0; i < n; i++) {
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for (int j = 0; j < n/2; j++) {
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int tmp = matrix[i][j];
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matrix[i][j] = matrix[i][n - j - 1];
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matrix[i][n - j - 1] = tmp;
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}
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}
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}
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}
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```
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