题解 | #顺时针旋转矩阵#

观察矩阵外圈，宏观想像

import java.util.*;

public class Solution {
    public int[][] rotateMatrix(int[][] mat, int n) {
        // write code here
        int x1 = 0, y1 = 0;
        int x2 = mat.length - 1, y2 = mat[0].length - 1;
        while (x1 <= x2 && y1 <= y2) {
            rotateEdge(mat, x1++, y1++, x2--, y2--);
        }
        return mat;
    }


    public void rotateEdge(int[][] m, int x1, int y1, int x2, int y2) {
        int temp = 0;
        for (int i = 0; i < x2 - x1; i++) {
            temp = m[x1][y1 + i];
            m[x1][y1 + i] = m[x2 - i][y1];
            m[x2 - i][y1] = m[x2][y2 - i];
            m[x2][y2 - i] = m[x1 + i][y2];
            m[x1 + i][y2] = temp;
        }
    }
}