北京大学机试 单词替换 Easy

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

vector<string>vec;

int main() {
	string s;
	string a,b;
	while (getline(cin,s)) {
		vec.resize(0);
		cin >> a >> b;
		stringstream fin(s);
		string c;
		while (fin >> c) {
			if (a == c) {
				vec.push_back(b);
			}
			else {
				vec.push_back(c);
			}
		}
		for (int i = 0; i < vec.size(); i++) {
			if (i == 0)
				cout << vec[i];
			else
				cout << " " << vec[i];
		}
		cout << endl;
		getchar();
	}

}