#include <stdio.h>
#include <iostream>
#include <string.h>
using namespace std;
char s[1005],a[105],b[105];
int main()
{
	cin.getline(s,1000);
	cin >> a;
	cin >> b;
	int len = strlen(s);
	int lena = strlen(a);
	for(int i = 0 ; i < len ; i++)
	{
		if(i == 0 || s[i-1] == ' ')
		{
			int id1,id2;
			id1 = i;
			id2 = 0;
			while(s[id1] == a[id2] && id2 < lena && id1 < len)
			{
				id1++,id2++;
			}
			if( id2 == lena && (s[id1] == ' ' || s[id1] == '\0') )
			{
				cout << b;
				if(s[id1] != '\0')
					cout << " ";
				i = id1;
				continue;
			}
			cout << s[i];
			
		}
		else 
		{
			cout << s[i];
		}
	}
	// cout << endl;
}

main函数部分如下:

int main()
{
	getline(cin, str);
	cin >> i >> j;
	str =  " " + str + " ";
	i =  " " + i + " ";
	j =  " " + j + " ";
	while(str.find(i, pos) != str.npos){
		pos = str.find(i, pos);
		str.replace(pos, i.size(), j);
		pos ++;
	}
	str.erase(0, 1);
	cout << str << endl;
	return 0;
}

#include<bits/stdc++.h>
using namespace std;
const int N=1e5+10;
const int INF=0x3f3f3f3f;
int main(){
	string s,a,b;
	getline (cin,s);
	cin>>a>>b;
	s=" "+s+" ";
	a=" "+a+" ";
	b=" "+b+" ";
	while(s.find(a)!=string::npos){
		s.replace(s.find(a),a.size(),b);
	}
	for(int i=1;i<s.size()-1;i++){
		cout<<s[i];
	}
}

#include <iostream>
#include<cstring>
#include<bits/stdc++.h>
using namespace std;
char k[1145],a[114],b[114];
int main()
{
	cin.getline(k,1000);
	cin >> a;
	cin >> b;
	int len = strlen(k);
	int lena = strlen(a);
	for(int i = 0 ; i < len ; i++)
	{
		if(i == 0 || k[i-1] == ' ')
		{
			int id1,id2;
			id1 = i;
			id2 = 0;
			while(k[id1] == a[id2] && id2 < lena && id1 < len)
			{
				id1++,id2++;
			}
			if( id2 == lena && (k[id1] == ' ' || k[id1] == '\0') )
			{
				cout << b;
				if(k[id1] != '\0')
					cout << " ";
				i = id1;
				continue;
			}
			cout << k[i];
			
		}
		else 
		{
			cout << k[i];
		}
	}
}