Java经典编程习题100例：第20例：求一个3*3矩阵对角线元素之和

对角线遍历循环

public class Main {
    public static void main(String[] args) {
        int[][] arr = new int[3][3];
        int k = 1;
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                arr[i][j] = k++;
            }
        }
        int res = 0;
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) {
                if (i == j) {
                    res += arr[i][j];
                }
            }
        }
        System.out.println("结果：" + res);
    }
}