洛谷 P5658 括号树

自己没什么思路，就看了看第一篇题解，简直不要讲的太好！自愧不如，下面给出链接，去看他吧！
墨攸的题解 P5658 【括号树】

(50pts)

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;

const int A = 5e5 + 11;
const int B = 1e6 + 11;
const int mod = 1e9 + 7;
const int inf = 0x3f3f3f3f;

inline int read() {
	char c = getchar(); int x = 0, f = 1;
	for( ; !isdigit(c); c = getchar()) if(c == '-') f = -1;
	for( ; isdigit(c); c = getchar()) x = x * 10 + (c ^ 48);
	return x * f;
}

struct node {
	int nxt, to;
} e[A << 1];
int n, cnt, head[A], f[A], ans[A], top = 0;
char sta[A], ss[A], a[A];

inline void add(int from, int to) {
	e[++cnt].to = to;
	e[cnt].nxt = head[from];
	head[from] = cnt;
}

int jisuan() {
	int tp = 0, res = 0;
	for(int i = top; i >= 1; i--) {
		if(sta[i] == ')') ++tp;
		else {
			if(tp > 0) tp--;
			else break;
		}
		if(tp == 0) res++;
	}
	return res;
}

void dfs(int now, int fa) {
	for(int i = head[now]; i; i = e[i].nxt) {
		int to = e[i].to;
		sta[++top] = a[to];
		if(a[to] == '(') ans[to] = ans[now];
		else ans[to] = ans[now] + jisuan();
		dfs(to, now);
		top--;
	}
}

int main() {
	n = read(); scanf("%s", a + 1);
	for(int i = 2, x; i <= n; i++) {
		x = read();
		f[i] = x;
		add(x, i);
	}
	sta[++top] = a[1];
	dfs(1, 0);
	int sum = 0;
	for(int i = 1; i <= n; i++) {
		sum ^= (i * ans[i]);
	}
	cout << sum << '
';
	return 0;
}

(100pts):

/*
Author:loceaner
*/
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;

const int A = 5e5 + 11;
const int B = 1e6 + 11;
const int mod = 1e9 + 7;
const int inf = 0x3f3f3f3f;

inline int read() {
	char c = getchar(); int x = 0, f = 1;
	for( ; !isdigit(c); c = getchar()) if(c == '-') f = -1;
	for( ; isdigit(c); c = getchar()) x = x * 10 + (c ^ 48);
	return x * f;
}

char s[A];
long long ans, f[A], sum[A];
struct node { int to, nxt; } e[A];
int n, cnt, top, fa[A], sta[A], head[A];

inline void add(int from, int to) {
	e[++cnt].to = to;
	e[cnt].nxt = head[from];
	head[from] = cnt;
}

void dfs(int x) {
	int tmp = 0;
	if (s[x] == ')') {
		if (top) tmp = sta[top--], f[x] = f[fa[tmp]] + 1;
	}
	else sta[++top] = x;
	sum[x] = sum[fa[x]] + f[x];
	for (int i = head[x]; i; i = e[i].nxt) dfs(e[i].to);
	if (tmp) sta[++top] = tmp;
	else if (top) top--;
}

int main() {
	n = read();
	scanf("%s", s + 1);
	for (int i = 2; i <= n; i++) add(fa[i] = read(), i);
	dfs(1);
	for (int i = 1; i <= n; i++) ans ^= sum[i] * i * 1ll;
	cout << ans << '
';
	return 0;
}