題目描述：

刪除第一個字符串中出現的第二個字符串，比如s1：ababaabb, s2:aba，輸出應為：baabb

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

int main(){
    string s1, s2;
    while(cin >> s1){
        char c = getchar();
        cin >> s2;
        int pos = -1;
        while((pos = s1.find(s2)) >= 0){
            //cout << pos << endl;
            s1.erase(pos, s2.size());
            pos = -1;
        }
        cout << s1 << endl;
    }
    return 0;

}
 

s1.find(s2): return the position where s2 appear in s1. eg:s1 = "ababaabbab", s2 = "aab", and the result is 4;
s1.find(ch): return the position where char ch appear in s1.
s1.erase(pos, size): delete the char form pos to pos + size - 1; And return the s1 changed.
s1.erase(pos): delete from the pos until the end.
 

刪除第一個字符串出現的第二個字符串