https://www.hackerrank.com/challenges/reduced-string/problem
He wants to reduce the string to its shortest length by doing a series of operations in which he selects a pair of adjacent lowercase letters that match, and then he deletes them.
aaabccddd->abccddd->abddd->abd
aabb->""
#include <iostream>
#include <string>
using namespace std;
int main()
{
string s;
cin >> s;
for (int i = 0; i < (int)(s.length() - 1); i++){
if (!s.empty()&&s[i] == s[i + 1]){
s.erase(i, 2);
i = -1;//后面I还要加1，从头开始
}
}
if (s.empty()){
cout << "EMPTY" << endl;
}
else{
cout << s << endl;
}
return 0;
}