hdu 4607 Park Visit

求出树的直径d。当k<=d的时候，显然直接在直径上走就行了，当k>d的时候，便是直径d的长度 加上 多出来的点数*2.

#include<iostream>#include<algorithm>#include<vector>#include<cstdio>#include<cstring>#define FF(i, a ,b) for(int i=a; i<b; i++)#define FD(i, a ,b) for(int i=a; i>b; i--)#define REP(i, n) for(int i=0; i<n; i++)#define LL long long#define CLR(a, b) memset(a, b, sizeof(a))#define PB push_backusing namespace std;const int maxn = 111111;int n, m, dist, k, end;vector<int> G[maxn];void dfs(int x, int fa, int d){    int nc = G[x].size();    if(nc == 1)    {        if(d > dist)        {            dist = d;            end = x;        }    }    REP(i, nc)    {        int v = G[x][i];        if(v != fa)        {            dfs(v, x, d+1);        }    }}int main(){    int T, a, b;    scanf("%d", &T);    while(T--)    {        scanf("%d%d", &n, &m);        REP(i, n+1) G[i].clear();        FF(i, 1, n)        {            scanf("%d%d", &a, &b);            G[a].PB(b);            G[b].PB(a);        }        dist = 0;        dfs(1, -1, 0);        dfs(end, -1, 0);        dist++;        while(m--)        {            scanf("%d", &k);            if(k <= dist) printf("%d\n", k-1);            else printf("%d\n", dist - 1 + (k-dist)*2);        }    }    return 0;}