并查集 Destroying Array CodeForces - 722C 和 Islands UVA - 1665

最新推荐文章于 2025-08-08 11:25:43 发布

原创最新推荐文章于 2025-08-08 11:25:43 发布 · 254 阅读

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两题比较类似，就是连通块，另外，并查集两种初始化方式

destroying array，还有一种思路是把所有连通块的和加到集合里面，对于一个新元素，如果和已有连通块相邻，取出该连通块的值

加入新值，else 直接加

#include <iostream>
#include <string>
#include <cstring>
#include <string.h>
#include <sstream>
#include <stdio.h>
#include <set>
#include <sstream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <stack>
#include <time.h>
#include <math.h>
#include <map>
using namespace std;
#define ctime								printf("Time used = %.2f\n", (double)clock() / CLOCKS_PER_SEC);
#define fast                                ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define _for(i,a,b)                         for(int i = a;i < b;i++)
#define _rep(i,a,b)                         for(int i = a;i <= b;i++)
#define all(s)                              s.begin(), s.end()
#define local								freopen("in.txt", "r", stdin);freopen("out.txt", "w", stdout);
#define ll									long long
#define fi									first
#define	se									second

const int INF = 1e9;
const int maxn = 1e5 + 100;

int n, a[maxn], b[maxn], par[maxn], dx[] = { 1,-1 };
ll ma[maxn], ans[maxn];
bool vis[maxn] = { false };

int find(int x) {
	if (par[x] == -1) return -1;
	if (par[x] == x)
		return x;
	else return par[x] = find(par[x]);
}

int main() {
	//local
	scanf("%d", &n);
	for (int i = 1; i <= n; i++) {
		scanf("%d", a + i);
		//par[i] = i;
		ma[i] = a[i];
	}
	for (int i = 1; i <= n; i++)
		scanf("%d", b + i);
	ll all = 0,sum;
	memset(par, -1, sizeof(par));
	for (int i = n; i > 1; i--) {
		//vis[b[i]] = true;
		par[b[i]] = b[i];
		for (int j = 0; j < 2; j++) {
			int nx = b[i] + dx[j];
			if (0 < nx && nx <= n ) {
				int p = find(nx);
				if (p == -1) continue;
				int pre = find(b[i]);
				if (p != pre) {
					par[pre] = p;
					ma[p] += ma[pre];
				}

			}
		}
		all = max(all, ma[find(b[i])]);
		ans[i] = all;
	}
	for (int i = 2; i <= n; i++)
		cout << ans[i] << endl;
	cout << 0 << endl;
}

就这样吧，自己慢慢调就ok了