#include<bits/stdc++.h>
using namespace std;
string s;
const int N = 1e5+5;
//int a0[N] = {0};
//int a1[N] = {0};
int main(){
	cin >> s;
	int ans = 0;
	//int n = s.size();
	int l = 0, r = 0;
	int n = s.size()-1;
	int a0 = 0;
	int a1 = 0;
	while(r <= n && l <= n){
		ans = max(ans, a0-a1);
		//if(s[l] == '1') a1--;
		//else a0--;
		//cout << l << " " << r << endl;
		//r++;
		if(a0 < a1){
			if(s[l] == '1')
				a1--;
			else
				a0--;
			l++;
		}else{
			if(s[r] == '1')
				a1++;
			else
				a0++;
			r++;
		}
			
	}
	cout << ans;
}

萌新第一天学C艹， 80分代码求调！

来帮忙看看双向指针为什么只有80分