【BestCoder】 HDOJ 5102 The K-th Distance

按题解所说广搜就行。。。。

#include <iostream>
#include <queue> 
#include <stack> 
#include <map> 
#include <set> 
#include <bitset> 
#include <cstdio> 
#include <algorithm> 
#include <cstring> 
#include <climits>
#include <cstdlib>
#include <cmath>
#include <time.h>
#define maxn 200005
#define maxm 1000005
#define eps 1e-10
#define mod 1000000007
#define INF 999999999
#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
#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;}
void scanf(int &__x){__x=0;char __ch=getchar();while(__ch==' '||__ch=='\n')__ch=getchar();while(__ch>='0'&&__ch<='9')__x=__x*10+__ch-'0',__ch = getchar();}
LL gcd(LL _a, LL _b){if(!_b) return _a;else return gcd(_b, _a%_b);}
// head

struct Edge
{
	int v;
	Edge *next;
}pool[maxm], *H[maxn], *edges;

struct node
{
	int u, v, x;
	node(int u = 0, int v = 0, int x = 0) : u(u), v(v), x(x) {}
};
node q[2200005];
int n, k, f, r;

void addedges(int u, int v)
{
	edges->v = v;
	edges->next = H[u];
	H[u] = edges++;
}

void init(void)
{
	f = r = 0;
	edges = pool;
	memset(H, 0, sizeof H);
}

void read(void)
{
	int u, v;
	scanf("%d%d", &n, &k);
	k *= 2;
	for(int i = 1; i < n; i++) {
		scanf("%d%d", &u, &v);
		addedges(u, v);
		addedges(v, u);
		q[r++] = node(u, v, 1);
		q[r++] = node(v, u, 1);
	//	q.push(node(u, v, 1));
	//	q.push(node(v, u, 1));
	}
}

void work(void)
{
	LL ans = 0;
	while(f < r && f < k) {
		node t = q[f++];
		int u = t.u, v = t.v, x = t.x;
		ans += x;
		if(r >= k) continue;
		for(Edge *e = H[u]; e; e = e->next) if(e->v != v)
			q[r++] = node(e->v, u, x + 1);
	}
	ans /= 2;
	printf("%I64d\n", ans);
}

int main(void)
{
	int _;
	while(scanf("%d", &_)!=EOF) {
		while(_--) {
			init();
			read();
			work();
		}
	}

	return 0;
}