poj 1741

来源：互联网发布：新开淘宝店如何进货编辑：程序博客网时间：2024/06/05 02:44
#include <iostream>#include <algorithm>#include <cstring>#include <string>#include <cstdio>#include <cmath>#include <queue>#include <map>#include <set>#define eps 1e-5#define MAXN 11111#define MAXM 55555#define INF 1000000000using namespace std;struct EDGE{    int v, next, w;}edge[MAXM];int head[MAXN], e;int n, k, vis[MAXN], ans, root, num;void init(){    memset(vis, 0, sizeof(vis));    memset(head, -1, sizeof(head));    e = ans = 0;}void add(int u, int v, int w){    edge[e].v = v;    edge[e].w = w;    edge[e].next = head[u];    head[u] = e++;}int mx[MAXN], size[MAXN], mi, dis[MAXN];void dfssize(int u, int fa) //处理子树的大小{    size[u] = 1;    mx[u] = 0;    for(int i = head[u]; i != -1; i = edge[i].next)    {        int v = edge[i].v;        if(v != fa && !vis[v])        {            dfssize(v, u);            size[u] += size[v];            if(size[v] > mx[u]) mx[u] = size[v];        }    }}void dfsroot(int r, int u, int fa) //求重心{    if(size[r] - size[u] > mx[u]) mx[u] = size[r] - size[u];    if(mx[u] < mi) mi = mx[u], root = u;    for(int i = head[u]; i != -1; i = edge[i].next)    {        int v = edge[i].v;        if(v != fa && !vis[v]) dfsroot(r, v, u);    }}void dfsdis(int u, int d, int fa) //求距离{    dis[num++] = d;    for(int i = head[u]; i != -1; i = edge[i].next)    {        int v = edge[i].v;        if(v != fa && !vis[v]) dfsdis(v, d + edge[i].w, u);    }}int calc(int u, int d){    int ret = 0;    num = 0;    dfsdis(u, d, 0);    sort(dis, dis + num);    int i = 0, j = num - 1;    while(i < j) //二分求之    {        while(dis[i] + dis[j] > k && i < j) j--;        ret += j - i;        i++;    }    return ret;}void dfs(int u){    mi = n;    dfssize(u, 0);    dfsroot(u, u, 0);    ans += calc(root, 0);    vis[root] = 1;    printf("root==%d\n",root);    for(int i = head[root]; i != -1; i = edge[i].next)    {        int v = edge[i].v;        if(!vis[v])        {            ans -= calc(v, edge[i].w);            dfs(v);        }    }}int main(){    while(scanf("%d%d", &n, &k) != EOF)    {        if(!n && !k) break;        init();        int u, v, w;        for(int i = 0; i < n - 1; i++)        {            scanf("%d%d%d", &u, &v, &w);            add(u, v, w);            add(v, u, w);        }        dfs(1);        printf("%d\n", ans);    }    return 0;}
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