评测记录https://www.luogu.com.cn/record/88356276

#include <iostream>
#include <cmath>
#include <algorithm>
#include <cstring>
#include <iomanip>
#define LL long long 
using namespace std;
const int N=1e5+5;
int n,a[N],s[N],ans,Index[2*N];
int main()
{
	scanf("%d",&n);
	memset(Index,-1,sizeof(Index));
	for(int i=1;i<=n;++i){
		cin>>a[i];
		if(a[i]==0) a[i]=-1;
		s[i]=s[i-1]+a[i];
		if(Index[s[i]+100000]==-1)
		Index[s[i]+100000]=i;
	}
	for(int i=2;i<=n;++i){
		ans=max(ans,i-Index[s[i]+100000]);
	}
	printf("%d\n",ans);
	return 0;
}