C++ 代码
#include<cstdio>
#include<iostream>
#include<cstring>
using namespace std;
int main(){
string s,s1,s2,s3;
getline(cin,s);
cin>>s1>>s2;
for(int i=0;i<s.size();i++){
if(s[i]!=' '){
s3+=s[i];
}
else{
if(s3==s1){
cout<<s2;
s3="";
cout<<" ";
}
else{
cout<<s3;
s3="";
cout<<" ";
}
}
}
if(s3!="" && s3!=s1){
cout<<s3;
}
else if(s3!="" && s3 == s1){
cout<<s2;
}
return 0;
}