二位数组的主对角线相加

#include<stdio.h>
int main(){
//列0 1 2 //行
int date[4][5] = { { 5, 10, 20 }//0
, { 20, 5, 5 }//1
, { 30, 10, 20 }//2
, { 50, 20, 60 } };//3
int sum = 0,i,m;
for (i = 0; i < 3; i++){
for (m = 0; m < 3; m++) {
if (m == i){
sum += date[i][m];
}
}
}
printf("sum=%d\n", sum);
return 0;
}