Codeforces Round #402 (Div. 2) D. String Game(二分)

#include <bits/stdc++.h>
#define maxn 200005
using namespace std;
string s,str;
int pre[maxn];
int num,s_len,len;

bool Check(int xx){
	string ch = str;
	for(int i=1;i<=xx;i++){
		ch[pre[i] - 1] = '.';
	}
	int j = 0;
	for(int i=0;i<len;i++){
		if(ch[i] == s[j]){
			j++;
		}
		if(j == s_len)break;
	}
	if(j == s_len)return true;
	else return false;
}

int main()
{
	cin>>str;
	cin>>s;
	len = str.length();
	s_len = s.length();
	for(int i=1;i<=len;i++){
		scanf("%d",&pre[i]);
	}
	int l = 0, r = len, mid, ans;
	while(l <= r){
		mid = (l + r) >> 1;
		if(Check(mid)){
			ans = mid;
			l = mid + 1;
		}
		else r = mid - 1;
	}
	printf("%d\n", ans);
	return 0;
}