题解 | #顺时针旋转矩阵#

import java.util.*;

public class Solution {

//与顺时针打印矩阵相类似，确定左上和右下边界，由外向里将各边界上的数进行旋转

public int[][] rotateMatrix(int[][] mat, int n) {
    // write code here
    int firstLeft = 0;
    int firstRight = 0;
    int lastLeft = n - 1;
    int lastRight = n - 1;
    while(firstLeft <= lastLeft && firstRight <= lastRight){
        rotate(mat, firstLeft++, firstRight++, lastLeft--, lastRight--);
    }
    return mat;
}

public static void rotate(int[][] mat, int firstLeft, int firstRight, int lastLeft, int lastRight){
    int times = lastLeft - firstLeft;
    int tmp = 0;
    for(int i = 0; i < times; i++){
        tmp = mat[firstLeft][firstRight + i];
        mat[firstLeft][firstRight + i] = mat[lastLeft - i][firstRight];
        mat[lastLeft - i][firstRight] = mat[lastLeft][lastRight - i];
        mat[lastLeft][lastRight - i] = mat[firstLeft + i][lastRight];
        mat[firstLeft + i][lastRight] = tmp;
    }
}

}