適当にインデントしといて
[1]
#include<stdio.h>
int main(){int a=10,b=20;a+=b;b=a-b;a-=b;printf("%d %d",a,b);}
[2]
#include<stdio.h>
int main(){char m[5][20]={"a","b","c","d","e"},n[5][20]={"A","B","C","D","E"};
    int i;for(i=0;i<5;++i)printf("%s %s\n",m[i],n[i]);}
[3]
#include<stdio.h>
#include<string.h>
int main(){char m[5][20]={"a","b","c","d","e"},n[5][20]={"A","B","C","D","E"};
    int i;for(i=0;i<5;++i)printf("%s\n",strcat(m[i],n[i]));}