洛谷 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 << '\n';
	return 0;
}

\(100pts\):

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define int long long
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, sum, sta[A];
char ss[A], a[A];

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

void dfs(int now, int faans, int top) {
	int tp = 0;
	if(a[now] == '(') sta[++top] = now;
	else if(a[now] == ')') {
		if(top == 0) ans[now] = 0;
		else ans[now] = ans[f[sta[top]]] + 1, tp = sta[top], faans += ans[now], top--;
	}
	sum = sum ^ (faans * now);
	for(int i = head[now]; i; i = e[i].nxt) {
		int to = e[i].to;
		dfs(to, faans, top);
	}
	if(tp) sta[++top] = tp;
}

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