[HAOI2006]聪明的猴子 BZOJ 2429 Kruskal

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<string>
#include<cmath>
#include<map>
#include<set>
#include<vector>
#include<queue>
#include<bitset>
#include<ctime>
#include<deque>
#include<stack>
#include<functional>
#include<sstream>
//#include<cctype>
//#pragma GCC optimize(2)
using namespace std;
#define maxn 200005
#define inf 0x7fffffff
//#define INF 1e18
#define rdint(x) scanf("%d",&x)
#define rdllt(x) scanf("%lld",&x)
#define rdult(x) scanf("%lu",&x)
#define rdlf(x) scanf("%lf",&x)
#define rdstr(x) scanf("%s",x)
typedef long long  ll;
typedef unsigned long long ull;
typedef unsigned int U;
#define ms(x) memset((x),0,sizeof(x))
const long long int mod = 1e9;
#define Mod 1000000000
#define sq(x) (x)*(x)
#define eps 1e-11
typedef pair<int, int> pii;
#define pi acos(-1.0)
//const int N = 1005;
#define REP(i,n) for(int i=0;i<(n);i++)
typedef pair<int, int> pii;

inline int rd() {
	int x = 0;
	char c = getchar();
	bool f = false;
	while (!isdigit(c)) {
		if (c == '-') f = true;
		c = getchar();
	}
	while (isdigit(c)) {
		x = (x << 1) + (x << 3) + (c ^ 48);
		c = getchar();
	}
	return f ? -x : x;
}

ll gcd(ll a, ll b) {
	return b == 0 ? a : gcd(b, a%b);
}
int sqr(int x) { return x * x; }

/*ll ans;
ll exgcd(ll a, ll b, ll &x, ll &y) {
	if (!b) {
		x = 1; y = 0; return a;
	}
	ans = exgcd(b, a%b, x, y);
	ll t = x; x = y; y = t - a / b * y;
	return ans;
}
*/

int m;
double rg[maxn<<2];
int n;
struct node {
	int x, y;
	double d;
}a[maxn<<2],e[maxn<<2];

int fa[maxn<<2];
void init() {
	for (int i = 0; i <= n; i++)fa[i] = i;
}
double dis(int a, int b, int x, int y) {
	return 1.0*sqrt((a - x)*(a - x) + (b - y)*(b - y));
}

int findfa(int x) {
	if (x == fa[x])return x;
	return fa[x] = findfa(fa[x]);
}

void merge(int p, int q) {
	int u = findfa(p);
	int v = findfa(q);
	if (u != v)fa[u] = v;
}
double ans = 0;
int tot = 0;
bool cmp(node a, node b) {
	return a.d < b.d;
}
void kruskal() {
	int cnt = 0;
	for (int i = 1; i <= tot; i++) {
		int u = e[i].x;
		int v = e[i].y;
		double d = e[i].d;
		if (findfa(u) != findfa(v)) {
			merge(u, v);
			ans = max(ans, d);
			cnt++;
			if (cnt >= n - 1)break;
		}
	}
}

int main() {
//	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	m = rd();
	for (int i = 1; i <= m; i++)rdlf(rg[i]);
	n = rd(); init();
	for (int i = 1; i <= n; i++)rdint(a[i].x), rdint(a[i].y);

	for (int i = 1; i <= n; i++) {
		for (int j = i + 1; j <= n; j++) {
			e[++tot].x = i;
			e[tot].y = j;
			e[tot].d = 1.0*dis(a[i].x, a[i].y, a[j].x, a[j].y);
		}
	}
	sort(e + 1, e + 1 + tot, cmp);
	kruskal();
	int num = 0;
	for (int i = 1; i <= m; i++) {
		if (rg[i] >= ans)num++;
	}
	cout << num << endl;
	return 0;
}