题解 | #单词替换#

#include<iostream>
#include<string>
using namespace std;

//习题4.2 单次替换
int main()
{
	string s, ss, sss;
	getline(cin, s);
	cin >> ss;
	cin >> sss;

	for (int i = 0; i < s.size() - ss.size(); i++) {
		string temp = s.substr(i, ss.size());
		if ((i==0 || s[i-1]==' ') && temp == ss && (s[i + ss.size()] == ' ' || (i + ss.size()) == s.size())) {
			s.replace(i, ss.length(), sss);
		}
	}

	cout << s << endl;

	return 0;
}