count largest substring with equal no.of zeros and one's ..O(n)

#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<string,int> psi;
typedef unordered_map<int,int> mii;
typedef unordered_map<long long,long long> mll;
typedef unordered_map<string,int> msi;
typedef unordered_map<char,int> mci;
typedef unordered_set<int> si;
typedef unordered_set<long long> sll;
typedef unordered_set<string> ss;
typedef unordered_set<char> sc;
typedef map<int,int> ormii;
typedef map<long long,long long> ormll;
typedef map<string,int> ormsi;
typedef map<char,int> ormci;
typedef set<int> orsi;
typedef set<long long> orsll;
typedef set<string> orss;
typedef set<char> orsc;
typedef vector<int> vi;
typedef vector<string> vs;
typedef vector<char> vc;
typedef vector<ll> vll;
typedef vector<vector<int>> vvi;
typedef vector<vector<string>> vvs;
typedef vector<vector<ll>> vvll;

#define FOR(i, a, b) for (auto i=a; i<=(b); i++)
#define FORd(i,b,a) for (int i =b; i >= a; i--)
#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define ins insert

const int MOD = 1000000007;
//type functions here
//O(n) solution
//data tested in vector v: {0},{1},{1,0},{1,0,0},{1,0,0,1},{1,0,0,1,1,1,1,1,1,1,0,0,0,1}


int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

	int tc=1;
	//cin>>tc;
	FOR(w,1,tc)
	{
	   vector<int> v={1,0,0,1,1,1,1,1,1,1,0,0,0,1};
	   int n=sz(v)-1;
	   int x=0,ans=0;
	   mii m;
	   m[0]=-1;
	   FOR(i,0,n)
	   {
	      x+=(v[i]==0?-1:1);
	      if(m.find(x)!=m.end()) ans=max(ans,i-m[x]);
	      else      m[x]=i;
	   }
	   cout<<ans<<endl;
	}
	return 0;
}