hihocoder #1168 : 运输货物

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这题挺考思维的。。。以出口为根，将树看成不同层，每次都是从下向上运输货物。。。。

#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 100005#define maxm 200005#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;}//headstruct Edge{int v;Edge *next;}*H[maxn], E[maxm], *edges;LL dis[maxn];int a[maxn];int dist, n, s;void init(){edges = E;memset(H, 0, sizeof H);}void addedges(int u, int v){edges->v = v;edges->next = H[u];H[u] = edges++;}void dfs(int u, int fa, int dep){if(a[u]) dist = max(dist, dep);dis[dep] += a[u];for(Edge *e = H[u]; e; e = e->next) if(e->v != fa) dfs(e->v, u, dep+1);}void work(int _){int u, v;scanf("%d%d", &n, &s);for(int i = 1; i < n; i++) {scanf("%d%d", &u, &v);addedges(u, v);addedges(v, u);}for(int i = 1; i <= n; i++) scanf("%d", &a[i]);dist = 0;LL ans = 0;for(Edge *e = H[s]; e; e = e->next) {int v = e->v;dist = 0;dfs(v, s, 0);LL t1 = 0, t2 = 0;for(int i = 0; i <= dist; i++) {t1 += dis[i];if(dis[i] == 0 && t1 + t2 <= i) t2++;dis[i] = 0;}ans = max(ans, t1 + t2);}printf("Case #%d: %lld\n", _, ans);}int main(){int _;scanf("%d", &_);for(int i = 1; i <= _; i++) {init();work(i);}return 0;}

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