string操作 + 分支语句

#include<bits/stdc++.h>
using namespace std;
int main(){
    char dna[260];
    cin>>dna;
    for(int i=0;i<strlen(dna);i++){
        if(dna[i]=='A') cout<<"T";
        else if(dna[i]=='T') cout<<"A";
        else if(dna[i]=='G') cout<<"C";
        else cout<<"G";
    }
    return 0;
}