简单的Stack
CODE:
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#include<vector>
#include<set>
#include<queue>
#include<map>
#include<sstream>
#include<iostream>
using namespace std;
#define FOR(i,a,b) for(int (i)=(a);(i)<=(b);(i)++)
#define DOR(i,a,b) for(int (i)=(a);(i)>=(b);(i)--)
#define bug puts("Fuck");
#define LL long long
#define pb push_back
#define mp make_pair
#define nMax 200010
#define eps 1e-8
#define inf 0x7fffffff
char st[nMax],s[nMax];
int main(){
#ifndef ONLINE_JUDGE
freopen("input.txt","r",stdin);
// freopen("output.txt","w",stdout);
#endif
while(gets(s)){
int top=0;
for(int i=0;s[i];i++) {
if(top==0 || s[i]!=st[top]) st[++top] = s[i];
else if(s[i] == st[top]) {
while(top && st[top]==s[i]) top--;
}
}
for(int i=1;i<=top;i++) printf("%c",st[i]);printf("\n");
}
return 0;
}