求二维数组周边元素之和
编写程序求出一个M行N列二维数组周边元素之和（用符号常量定义M为5，N为6）。
#include <stdio.h>#define M 5
#define N 6int main()
{int arr[M][N] = {0};int sum = 0;for (int i = 0; i < M; i++){for (int j = 0; j < N; j++){scanf("%d",&arr[i][j]);}}for (int i = 0; i < N; i++){sum += arr[0][i];}for (int i = 1; i < M; i++){sum += arr[i][0];}for (int i = 1; i < M; i++){sum += arr[i][N-1];}for (int i = 1; i < N - 1; i++){sum += arr[M-1][i];}printf("%d\\n",sum);return 0;
}
