Good String

用flag来调节奇数和偶数

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<vector>
#include<map>
#define MAXN 200010
int n,m1,m2,ans,nn;
char a[MAXN],tmp[MAXN];
using namespace std;
inline bool check()
{
    if(nn<=1) return true;
    for(int i=1;i<nn;i+=2)
    {
        if(a[i]==a[i+1]) return false;
    }
    return true;
}
inline void solve()
{
    int cnt=0;
    int flag=0;
    for(int i=1;i<=nn;i++,flag^=1)
    {
        if(i!=nn&&flag==0)
        {
            if(a[i]==a[i+1]) 
            {
                ans++;
                flag^=1;
                continue;
            }
        }
        tmp[++cnt]=a[i];
    }
    nn=cnt;
    for(int i=1;i<=nn;i++) a[i]=tmp[i];
    // printf("nn=%d\n",nn);
}
int main()
{
    #ifndef ONLINE_JUDGE
    freopen("ce.in","r",stdin);
    #endif
    scanf("%d",&n);
    scanf("%s",a+1);
    nn=n;
    if(check())
    {
        cout<<0<<endl;
        for(int i=1;i<=n;i++) cout<<a[i];
        cout<<endl;
        return 0;
    }
    while(check()==false)
        solve();
    if(nn&1) ans++,nn--;
    cout<<ans<<endl;
    for(int i=1;i<=nn;i++) cout<<a[i];
    cout<<endl;
    return 0;
}