转置矩阵+矩阵对角线元素和

867. 转置矩阵

class Solution {
    public int[][] transpose(int[][] matrix) {
        int m=matrix.length;
        int n=matrix[0].length;
        int[][] res=new int[n][m];
        int k=0;
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                res[j][i]=matrix[i][j];
            }
        }
        return res;
    }
}

1572. 矩阵对角线元素的和

class Solution {
    public int diagonalSum(int[][] mat) {
        int n = mat.length;
        int res = 0;
        for(int i = 0; i < n; i++){
            res += mat[i][i];
            res += mat[i][n-i-1];
        }
        if((n&1) == 0) return res;
        return res-mat[n/2][n/2];
    }
}