Codeforces 380C. Sereja and Brackets【线段树】

#include <iostream>
#include <cstdio>
#include <cstring>
#define N 1000010
using namespace std;
#define L(x) (x)<<1
#define R(x) (x)<<1|1
int m,len,r[N],l[N];
char bra[N];
struct node
{
    int ll,rr,v;
}t[N*6];
int bulid(int x,int y,int idx)
{
    t[idx].ll=x,t[idx].rr=y;
    if(x==y) return t[idx].v=l[x];
    int mid=(x+y)/2;
    return t[idx].v=min(bulid(x,mid,L(idx)),bulid(mid+1,y,R(idx)));
}
int query(int x,int y,int idx)
{
    if(x==t[idx].ll && y==t[idx].rr) return t[idx].v;
    int mid=(t[idx].ll+t[idx].rr)/2;
    if(x>mid) return query(x,y,R(idx));
    if(y<=mid) return query(x,y,L(idx));
    return min(query(x,mid,L(idx)),query(mid+1,y,R(idx)));
}
int main()
{
    scanf("%s",bra);
    len=strlen(bra);
    int tmp=0;
    for(int i=1;i<=len;i++)
    {
        r[i]=r[i-1];
        if(bra[i-1]=='(') tmp++;
        else if(tmp) r[i]++,tmp--;
        l[i]=tmp;
    }
    bulid(1,len,1);
    scanf("%d",&m);
    while(m--)
    {
        int a,b;
        scanf("%d%d",&a,&b);
        if(a==b) {cout<<0<<endl;continue;}
        int ans=min(r[b]-r[a-1],r[b]-r[a-1]-l[a-1]+query(a,b,1));
        cout<<ans*2<<endl;
    }
    return 0;
}