题解 | #单词替换#

# include<stdio.h>
#include<iostream>
using namespace std;
int main(){
	string s,tag,sub;
while(getline(cin,s)){
	cin>>sub;
	cin>>tag;
	int index = 0;
	int count = 0;
	while((index=s.find(sub,index))<s.length())//迭代
	{	
	  if((s[index-1]==' '&&s[index+sub.length()]==' ')||(index==0&&s[index+sub.length()]==' ')||(s[index-1]==' '&&index==s.length()-1))//1.单词在中间的情况  2.单词在最开头的情况 3.单词在最末尾的情况
			s.replace(index,sub.length(),tag);//替换 （index ,length ,"tag"）
		index++;
	}
	cout<<s;
	
	
}
	
}