Leetcode48.选择图像

题目链接：48. 旋转图像

思路：模拟。逐行旋转。

代码：

class Solution {
    public void rotate(int[][] matrix) {
        for(int i=0; i<((matrix.length + 1)>>1); i++){
            helper(matrix, i);
        }
    }
    private void helper(int[][] matrix, int rowIndex){
        int len = matrix.length - 1;
        for(int i=rowIndex; i<len-rowIndex; i++){
            int t = matrix[rowIndex][i];
            matrix[rowIndex][i] = matrix[len - i][rowIndex];
            matrix[len - i][rowIndex] = matrix[len - rowIndex][len - i];
            matrix[len - rowIndex][len - i] = matrix[i][len - rowIndex];
            matrix[i][len - rowIndex] = t;
        }
    }
}