编写一个求二维数组主对角线元素和的函数sum( ),在主函数中初始化数组...答:include <iostream>using namespace std;int sum(int a[][4]){int i,j,s=0;for(i=0;i<4;i++)for(j=0;j<4;j++)if(i==j) s+=a[i][j];return s;}int main(){int a[][4]={11,22,33,44,25,35,45,55,18,28,38,48,55,66,77,88};cout<<sum(a);return 0;} ...