旋转图像

川长思鸟来 2022-12-29 02:17 157阅读 0赞

> leetcode 48题 \[medium\]  
> 中：[旋转图像][Link 1]  
> 英：[Rotate Image][]  
> ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1NKMTU1MQ_size_16_color_FFFFFF_t_70]

### 题解1 ###

##### 1. 思路：从外层到里层一层一层旋转 #####

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1NKMTU1MQ_size_16_color_FFFFFF_t_70 1]

##### 2. 时间复杂度：O(n²) #####

##### 3. 空间复杂度：O(1) #####

##### 4. 实现 #####

/** * @param {number[][]} matrix * @return {void} Do not return anything, modify matrix in-place instead. */
    var rotate = function(matrix) { 
        let matrixLen = matrix.length;
        for(let layer=0, maxLayer=Math.floor(matrixLen/2); layer<maxLayer; layer++){ 
            for(let column=layer; column<matrixLen-layer-1; column++){ 
                // 旋转 (ES6 解构语法)
                [   
                    matrix[layer][column], 
                    matrix[column][matrixLen-1-layer], 
                    matrix[matrixLen-1-layer][matrixLen-1-column], 
                    matrix[matrixLen-1-column][layer]
                ] 
                = 
                [
                    matrix[matrixLen-1-column][layer],
                    matrix[layer][column], 
                    matrix[column][matrixLen-1-layer], 
                    matrix[matrixLen-1-layer][matrixLen-1-column]
                ]
            }
        }
    };

### 题解2 ###

##### 1. 思路：翻转 #####

1.  先水平翻转
2.  再转置（沿主对角线翻转）

##### 2. 时间复杂度：O(n²) #####

##### 3. 空间复杂度：O(1) #####

##### 4. 实现 #####

/** * @param {number[][]} matrix * @return {void} Do not return anything, modify matrix in-place instead. */
    var rotate = function(matrix) { 
        let matrixLen = matrix.length;
        
        // 先水平翻转
        for(let i=0, maxI=Math.floor(matrixLen/2); i<maxI; i++){ 
            [matrix[i], matrix[matrixLen-1-i]] = [matrix[matrixLen-1-i], matrix[i]];
        }
    
        // 再转置（沿主对角线翻转）
        for(let i=0; i<matrixLen; i++){ 
            for(let j=i+1; j<matrixLen; j++){ 
                [matrix[i][j], matrix[j][i]] = [matrix[j][i], matrix[i][j]];
            }
        }
    };

[Link 1]: https://leetcode-cn.com/problems/rotate-image/
[Rotate Image]: https://leetcode.com/problems/rotate-image/
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1NKMTU1MQ_size_16_color_FFFFFF_t_70]: /images/20221120/c37e73264b9840bd91f179445184116f.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1NKMTU1MQ_size_16_color_FFFFFF_t_70 1]: https://img-blog.csdnimg.cn/20201219155432159.png?x-oss-process=image/watermark,type_ZmFuZ3poZW5naGVpdGk,shadow_10,text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L1NKMTU1MQ==,size_16,color_FFFFFF,t_70