CodeForces 779D String Game

#include<map>
#include<set>
#include<ctime>
#include<cmath>
#include<queue>
#include<string>
#include<vector>
#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<functional>
using namespace std;

char s[200010],t[200010];
int x[200010];

char tmp[200010];

bool check(int p)
{
    memset(tmp,0,sizeof tmp);
    strcpy(tmp,s);

    for(int i=1;i<=p;i++) tmp[x[i]] =‘?‘;
    int len = strlen(t); int u=0;
    for(int i=0;tmp[i];i++)
    {
        if(tmp[i]==t[u]) u++;
        if(u==len) return 1;
    }
    return 0;
}

int main()
{
    scanf("%s%s",s,t); int n=strlen(s);
    for(int i=1;i<=n;i++)
    {
        scanf("%d",&x[i]);
        x[i]--;
    }

    int L=1,R=n,ans=0;
    while(L<=R)
    {
        int mid = (L+R)/2;
        if(check(mid)) ans=mid,L=mid+1;
        else R=mid-1;
    }
    printf("%d\n",ans);

    return 0;
}