ex10_2共同字符

//
//  main.cpp
//  ex10_2
//
//  Created by a007 on 17/12/1.
//  Copyright ? 2017年 a007. All rights reserved.
//

#include <iostream>
using namespace std;

string commonChars(const string &s1, const string &s2){
    string s3 = "";
    for (auto &character : s2) {    //对于s2中每一个元素
        if (s1.find(character) != s1.npos) {    //检查是否出现在s1中
            if (s3.find(character) == s3.npos) {    //检查是否已经出现在s3中，没有就加上，防止重复
                s3 += character;
            }
        }
    }
    return s3;
}

int main(int argc, const char * argv[]) {
    string s1, s2;
    cout << "Enter a string s1: ";
    getline(cin, s1);
    cout << "Enter a string s2: ";
    getline(cin, s2);
    
    string s3 = commonChars(s1, s2);
    if (s3 != "") {
        cout << "The common characters are " << s3 << endl;
    }else{
        cout << "No common characters" << endl;
    }
    
    return 0;
}