Codeforces 380C - Sereja and Brackets (线段树括号匹配)

C. Sereja and Brackets
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

Sereja has a bracket sequence s1,?s2,?...,?sn, or, in other words, a string s of length n, consisting of characters "(" and ")".

Sereja needs to answer m queries, each of them is described by two integers li,?ri (1?≤?li?≤?ri?≤?n). The answer to the i-th query is the length of the maximum correct bracket subsequence of sequence sli,?sli?+?1,?...,?sri. Help Sereja answer all queries.

You can find the definitions for a subsequence and a correct bracket sequence in the notes.

Input

The first line contains a sequence of characters s1,?s2,?...,?sn (1?≤?n?≤?106) without any spaces. Each character is either a "(" or a ")". The second line contains integer m (1?≤?m?≤?105) — the number of queries. Each of the next m lines contains a pair of integers. The i-th line contains integers li,?ri (1?≤?li?≤?ri?≤?n) — the description of the i-th query.

Output

Print the answer to each question on a single line. Print the answers in the order they go in the input.

Sample test(s)
input
())(())(())(
7
1 1
2 3
1 2
1 12
8 12
5 11
2 10
output
0
0
2
10
4
6
6

题意:给定一组括号,以下有m次询问,问一个区间有几个括号匹配。

思路:线段树,在向上传递值的时候,左区间的左括号和右区间的右括号能组成一个新括号传递上去。

代码:

#include <stdio.h>
#include <string.h>
#define max(a,b) ((a)>(b)?(a):(b))
#define min(a,b) ((a)<(b)?(a):(b))
const int N = 1000005;

int n, m;
char str[N];

struct Tree {
	int l, r, lv, rv, sum;
	Tree operator + (const Tree &a) {
		Tree h;
		h.sum = sum + a.sum; h.lv = lv + a.lv; h.rv = rv + a.rv;
		int num1 = min(lv, a.rv); 
		h.sum += num1 * 2; h.lv -= num1; h.rv -= num1;
		return h;
	}
}st[3 * N];

Tree build(int l, int r, int id) {
	if (l == r) {
		if (str[l] == ‘(‘) {
			st[id].lv = 1; st[id].rv = 0; st[id].sum = 0;
		}
		else {
			st[id].lv = 0; st[id].rv = 1; st[id].sum = 0;
		}
		st[id].l = l; st[id].r = r;
	}
	else {
		int mid = (l + r) / 2;
		st[id] = build(l, mid, id * 2) + build(mid + 1, r, id * 2 + 1);
		st[id].l = l; st[id].r = r;
	}
	return st[id];
}

Tree Query(int l, int r, int id) {
	if (l == st[id].l && r == st[id].r)
		return st[id];
	int mid = (st[id].l + st[id].r) / 2;
	if (l <= mid && r > mid)
		return Query(l, mid, 2 * id) + Query(mid + 1, r, 2 * id + 1);
	else if (l <= mid && r <= mid) {return Query(l, r, 2 * id);}
	else {return Query(l, r, 2 * id + 1);}
}

void init() {
	scanf("%s%d", str + 1, &m);
	n = strlen(str + 1);
	build(1, n, 1);
	int l, r;
	while (m--) {
		scanf("%d%d", &l, &r);
		printf("%d\n", Query(l, r, 1).sum);
	}
}

int main() {
	init();
	return 0;
}


Codeforces 380C - Sereja and Brackets (线段树括号匹配)

上一篇:Python使用MySQL数据库【转】


下一篇:如何将存储在MongoDB数据库中的数据导出到Excel中?