【并查集】 hihocoder #1160 : 攻城略地

先用并查集计算出连每一条边所能节省的代价，然后删掉前k条边，最后用并查集计算答案。。

#include <iostream>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <bitset>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <climits>
#include <cstdlib>
#include <math.h>
#include <time.h>
#define maxn 200005
#define maxm 400005
#define eps 1e-7
#define mod 1000000007
#define INF 0x3f3f3f3f
#define PI (acos(-1.0))
#define lowbit(x) (x&(-x))
#define mp make_pair
#define ls o<<1
#define rs o<<1 | 1
#define lson o<<1, L, mid 
#define rson o<<1 | 1, mid+1, R
#define pii pair<int, int>
#pragma comment(linker, "/STACK:16777216")
typedef long long LL;
typedef unsigned long long ULL;
//typedef int LL;
using namespace std;
LL qpow(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base;base=base*base;b/=2;}return res;}
LL powmod(LL a, LL b){LL res=1,base=a;while(b){if(b%2)res=res*base%mod;base=base*base%mod;b/=2;}return res;}
//head

struct Edge
{
	int u, v, cost;
}e[maxm];

int f[maxn];
int c[maxn];
int n, m, k;

int find(int u)
{
	return f[u] == u ? f[u] : f[u] = find(f[u]);
}

int merge(int a, int b)
{
	int aa = find(a), bb = find(b);
	if(aa != bb) {
		if(c[aa] > c[bb]) {
			f[aa] = bb;
			return c[aa];
		}
		else {
			f[bb] = aa;
			return c[bb];	
		}
	}
	else return 0;
}

int cmp(Edge a, Edge b)
{
	return a.cost < b.cost;
}

void work(int _)
{
	scanf("%d%d%d", &n, &m, &k);
	for(int i = 1; i <= n; i++) scanf("%d", &c[i]);
	for(int i = 1; i <= n; i++) f[i] = i;
	for(int i = 1; i <= m; i++) scanf("%d%d", &e[i].u, &e[i].v);
	for(int i = 1; i <= m; i++) e[i].cost = merge(e[i].u, e[i].v);
	sort(e+1, e+m+1, cmp);
	for(int i = 1; i <= n; i++) f[i] = i;
	for(int i = k+1; i <= m; i++) merge(e[i].u, e[i].v);
	LL ans = 0;
	for(int i = 1; i <= n; i++) if(find(i) == i) ans += c[i];
	printf("Case #%d: %lld\n", _, ans);
}

int main()
{
	int _;
	scanf("%d", &_);
	for(int i = 1; i <= _; i++) work(i);
	
	return 0;
}