#include<bits/stdc++.h>

using namespace std;

char a[300];

int main()

{

int g,i;

cin>>a;

g=strlen(a);

for(i=0;i<g;i++)

{

	if(a[i]=='A')

	a[i]=a[i]+19;

	else if(a[i]=='T')

	a[i]=a[i]-19;

	else if(a[i]=='C')

	a[i]=a[i]+4;

	else if(a[i]=='G')

	a[i]=a[i]-4;

}

cout<<a;

return 0;

}

思路

水题，根据题目说的写就行。

code

#include<bits/stdc++.h>
using namespace std;
int main(){
	string jjl;
	cin>>jjl;
	for(int i=0;i<jjl.size();i++){
		if(jjl[i]=='A')	cout<<'T';
		if(jjl[i]=='G')	cout<<'C';
		if(jjl[i]=='T')	cout<<'A';
		if(jjl[i]=='C')	cout<<'G';
	}
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
char a[10010];
int main()
{ 
     int ans=0;
    cin>>a;
    int len=strlen(a);
	for(int i=0;i<len;i++)
	{
		if(a[i]=='T') cout<<"A";
		if(a[i]=='A') cout<<"T";
		if(a[i]=='G') cout<<"C";
		if(a[i]=='C') cout<<"G";
	}
	return 0;
}