HDU 4729 An Easy Problem for Elfness(树上主席树+LCA+二分)

题目大意:给你一棵树,每条边有一个容量。然后m个询问,每个询问是互相独立的,给你两个点S, T,一个预算K,
建一条容量为1的新边的费用A(可以建在任一两个节点之间,包括S,T),将某一条现有的边容量扩大1的费用B。
问从S到T在预算允许的情况下最大流是多少。
这个分两种情况来讨论最优解:
1.如果 AB ,显然新建不会比扩展差,可以建立 kA 这么多条边。
2.如果 A>B ,这是有两种情况可能最优;第一种是新建然后对新建的边进行扩展;第二种则是对原路径上的边进行扩展;最后取两者最优即可。
这里第二种最多可以扩展的次数是 kB .
那么我们就二分答案and,如果路径长度 lmidai>kB ,显然只能是 ans<mid
否则就是 ansmid , ai 就是用主席树+LCA的事儿了。

/*****************************************
Author      :Crazy_AC(JamesQi)
Time        :2016
File Name   :
*****************************************/
// #pragma comment(linker, "/STACK:1024000000,1024000000")
#include <iostream>
#include <algorithm>
#include <iomanip>
#include <sstream>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <map>
#include <set>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <climits>
using namespace std;
#define MEM(x,y) memset(x, y,sizeof x)
#define pk push_back
#define lson rt << 1
#define rson rt << 1 | 1
#define bug cout << "BUG HERE\n"
#define debug(x) cout << #x << " = " << x << endl
#define ALL(v) (v).begin(), (v).end()
#define lowbit(x) ((x)&(-x))
#define Unique(x) sort(ALL(x)); (x).resize(unique(ALL(x)) - (x).begin())
#define BitOne(x) __builtin_popcount(x)
#define showtime printf("time = %.15f\n",clock() / (double)CLOCKS_PER_SEC)
#define Rep(i, l, r) for (int i = l;i <= r;++i)
#define Rrep(i, r, l) for (int i = r;i >= l;--i)
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int,int> ii;
typedef pair<ii,int> iii;
const double eps = 1e-8;
const double pi = 4 * atan(1);
const int inf = 1 << 30;
const int INF = 0x3f3f3f3f;
const int MOD = 1e9 + 7;
int nCase = 0;
//?????0???
int dcmp(double x){
   
   if (fabs(x) < eps) return 0;return x < 0?-1:1;}
template<class T> inline bool read(T &n){
    T x = 0, tmp = 1;
    char c = getchar();
    while((c < '0' || c > '9') && c != '-' && c != EOF) c = getchar();
    if(c == EOF) return false;
    if(c == '-') c = getchar(), tmp = -1;
    while(c >= '0' && c <= '9') x *= 10, x += (c - '0'),c = getchar();
    n = x*tmp;
    return true;
}
template <class T> inline void write(T n){
    if(n < 0){
   
   putchar('-');n = -n;}
    int len = 0,data[20];
    while(n){data[len++] = n%10;n /= 10;}
    if(!len) data[len++] = 0;
    while(len--) putchar(data[len]+48);
}
LL QMOD(LL x, LL k) {
    LL res = 1LL;
    while(k) {
   
   if (k & 1) res = res * x % MOD;k >>= 1;x = x * x % MOD;}
    return res;
}
int n, m;
const int maxn = 1e5 + 123;
int head[maxn], nxt[maxn*2], pnt[maxn*2], cap[maxn*2], ecnt;
inline void addedge(int u,int v,int c) {
    pnt[ecnt] = v, cap[ecnt] = c, nxt[ecnt] = head[u], head[u] = ecnt++;
    pnt[ecnt] = u, cap[ecnt] = c, nxt[ecnt] = head[v], head[v] = ecnt++;
}
struct Query {
    int s, t, k, a, b;
    void read() { scanf("%d%d%d%d%d", &s, &t, &k, &a, &b); }
}Q[maxn];
struct _LCA {
    const static int LOGN = 20;
    int dep[maxn], fa[LOGN][maxn];
    void dfs(int u,int f, int depth) {
   
   /*u = 1, f = -1, depth = 0*/
        fa[0][u] = f, dep[u] = depth;
        for (int i = head[u];~i;i = nxt[i]) {
            int v = pnt[i];
            if (v == f) continue;
            dfs(v, u, depth + 1);
        }
    }
    void build(int n) {
        for (int k = 0;k < LOGN;++k) {
            for (int u = 1;u <= n;++u) {
                if (fa[k][u] == -1) fa[k + 1][u] = -1;
                else fa[k + 1][u] = fa[k][fa[k][u]];
            }
        }
    }
    int upslop(int u,int p) {
        for (int k = 0;k < LOGN;++k)
            if ((p>>k) & 1) u = fa[k][u];
        return u;
    }
    int LCA(int u,int v) {
        if (dep[u] < dep[v]) swap(u, v);
        u = upslop(u, dep[u] - dep[v]);
        if (u == v) return u;
        for (int k = LOGN - 1;k >= 0;--k)
            if (fa[k][u] != fa[k][v]) {u = fa[k][u], v = fa[k][v];}
        return fa[0][u];
    }
}lca;
int root[maxn], ls[maxn*30], rs[maxn*30], tot;
LL sum[maxn*30], _cnt[maxn*20];
void build(int &rt, int l, int r) {
    rt = ++tot;
    sum[rt] = 0;
    _cnt[rt] = 0;
    if (l == r) return ;
    int mid = (l + r) >> 1;
    build(ls[rt], l, mid);
    build(rs[rt], mid + 1, r);
}
void updata(int last,int &rt, int l, int r,int pos, int val) {
    rt = ++tot;
    ls[rt] = ls[last], rs[rt] = rs[last];
    sum[rt] = sum[last] + 1, _cnt[rt] = _cnt[last] + val;
    if (l == r) return ;
    int mid = (l + r) >> 1;
    if (pos <= mid) updata(ls[last], ls[rt], l, mid, pos, val);
    else updata(rs[last], rs[rt], mid + 1, r, pos, val);
}
void dfs_build(int u,int f, int v) {
    updata(root[f], root[u], 0, 10000, v, v);
    for (int i = head[u];~i;i = nxt[i]) {
        if (pnt[i] == f) continue;
        dfs_build(pnt[i], u, cap[i]);
    }
}
int Query_Kth (int x, int y, int lca, int l, int r, int k) {
    while(l < r) {
        int mid = (l + r) >> 1;
        /*[l, mid]*/
        int temp = sum[ls[x]] + sum[ls[y]] - 2*sum[ls[lca]];
        // printf("[l = %d, r = %d, temp = %d]\n", l, r, temp);
        // printf("sum_lx = %lld, sum_ly = %lld, sum_l_lca = %lld\n", sum[ls[x]], sum[ls[y]], sum[ls[lca]]);
        if (k <= temp) {
            x = ls[x], y = ls[y], lca = ls[lca];
            r = mid;
        }else {
            k -= temp;
            x = rs[x], y = rs[y], lca = rs[lca];
            l = mid + 1;
        }
    }
    return l;
}
int Query(int x, int y,int lca, int l, int r,int cap) {
    int ret = 0;
    LL cnt = 0, res = 0;
    while(l < r) {
        int mid = (l + r) >> 1;
        /*[l, mid]*/
        LL temp_sum = sum[ls[x]] + sum[ls[y]] - 2LL*sum[ls[lca]];
        LL temp_cnt = _cnt[ls[x]] + _cnt[ls[y]] - 2LL*_cnt[ls[lca]];
        if ((temp_sum + res)*mid - (temp_cnt + cnt) > cap) {
            x = ls[x], y = ls[y], lca = ls[lca], r = mid;
        }else {
            ret = mid;
            x = rs[x], y = rs[y], lca = rs[lca];
            l = mid + 1;
            res += temp_sum;
            cnt += temp_cnt;
        }
    }
    return ret;
}
int main(int argc, const char * argv[])
{    
    // freopen("in.txt","r",stdin);
    // freopen("out.txt","w",stdout);
    // ios::sync_with_stdio(false);
    // cout.sync_with_stdio(false);
    // cin.sync_with_stdio(false);
    // cout << (1 << 19) << endl;
    int kase;cin >> kase;
    while(kase--) {
        memset(head, -1, sizeof head), ecnt = tot = 0;
        scanf("%d%d", &n, &m);
        for (int i = 1, u, v, c;i < n;++i) {
            scanf("%d%d%d", &u, &v, &c);
            addedge(u, v, c);
        }
        lca.dfs(1, -1, 0);
        lca.build(n);
        Rep(i, 1, m) Q[i].read();
        build(root[0], 0, 10000);
        dfs_build(1, 0, 0);/*u, fa*/
        printf("Case #%d:\n", ++nCase);
        Rep(i, 1, m) {
            // printf("[s = %d, t = %d, lca = %d]\n", Q[i].s, Q[i].t, lca.LCA(Q[i].s, Q[i].t));
            LL ans = (LL)Query_Kth(root[Q[i].s], root[Q[i].t], root[lca.LCA(Q[i].s, Q[i].t)], 0, 10000, 1);
            // debug(ans);
            if (Q[i].a < Q[i].b) ans += Q[i].k / Q[i].a;
            else {
                if (Q[i].k >= Q[i].a) ans += (Q[i].k - Q[i].a) / Q[i].b + 1;
                // debug(ans);
                ans = max(ans, (LL)Query(root[Q[i].s], root[Q[i].t], root[lca.LCA(Q[i].s, Q[i].t)], 0, 10000, Q[i].k / Q[i].b));
            }
            printf("%lld\n", ans);
        }
    }

    // showtime;
    return 0;
}

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转载自blog.csdn.net/KIJamesQi/article/details/52294514