bzoj3545 Peaks

题意：多次求从点x出发经过边权不超过k的边能走到的点中第k大的权值。

解：离线排序 + 并查集 + 线段树合并。

题面有锅...是第k大的权值不是第k大的山。

#include <cstdio>
#include <algorithm>

const int N = 100010, M = 500010, V = 7000010;

struct Edge {
    int x, y, h;
    inline bool operator <(const Edge &w) const {
        return h < w.h;
    }
}edge[M];

struct Ask {
    int x, h, k, id;
    inline bool operator <(const Ask &w) const {
        return h < w.h;
    }
}ask[M];

int fa[N], rt[N], ls[V], rs[V], sum[V], siz[N], tot, ans[M], X[N], val[N];

int find(int x) {
    if(x == fa[x]) {
        return x;
    }
    return fa[x] = find(fa[x]);
}

int merge(int x, int y) {
    if(!x || !y) {
        return x | y;
    }
    int o = ++tot;
    sum[o] = sum[x] + sum[y];
    ls[o] = merge(ls[x], ls[y]);
    rs[o] = merge(rs[x], rs[y]);
    return o;
}

int query(int k, int l, int r, int o) {
    if(l == r) {
        return r;
    }
    int mid = (l + r) >> 1;
    if(k > sum[rs[o]]) {
        return query(k - sum[rs[o]], l, mid, ls[o]);
    }
    else {
        return query(k, mid + 1, r, rs[o]);
    }
}

inline void Xmerge(int x, int y) {
    x = find(x);
    y = find(y);
    if(x == y) {
        return;
    }
    fa[y] = x;
    siz[x] += siz[y];
//    printf("siz %d += %d = %d 
", x, siz[y], siz[x]);
    rt[x] = merge(rt[x], rt[y]);
    return;
}

void insert(int p, int l, int r, int &o) {
    if(!o) {
        o = ++tot;
    }
    sum[o] = 1;
    if(l == r) {
        return;
    }
    int mid = (l + r) >> 1;
    if(p <= mid) {
        insert(p, l, mid, ls[o]);
    }
    else {
        insert(p, mid + 1, r, rs[o]);
    }
    return;
}

int main() {
    int n, m, q;
    scanf("%d%d%d", &n, &m, &q);
    for(int i = 1; i <= n; i++) {
        scanf("%d", &val[i]);
        X[i] = val[i];
    }
    std::sort(X + 1, X + n + 1);
    int xx = std::unique(X + 1, X + n + 1) - X - 1;
    for(int i = 1; i <= n; i++) {
        val[i] = std::lower_bound(X + 1, X + xx + 1, val[i]) - X;
        insert(val[i], 1, xx, rt[i]);
        fa[i] = i; siz[i] = 1;
    }
    for(int i = 1; i <= m; i++) {
        scanf("%d%d%d", &edge[i].x, &edge[i].y, &edge[i].h);
    }
    for(int i = 1; i <= q; i++) {
        scanf("%d%d%d", &ask[i].x, &ask[i].h, &ask[i].k);
        ask[i].id = i;
    }
    std::sort(edge + 1, edge + m + 1);
    std::sort(ask + 1, ask + q + 1);
    
    int p = 1;
    for(int i = 1; i <= q; i++) {
        while(p <= m && edge[p].h <= ask[i].h) {
            Xmerge(edge[p].x, edge[p].y);
            p++;
//            printf("Xmerge %d %d 
", edge[p].x, edge[p].y);
        }
        int x = find(ask[i].x);
//        printf("x = %d 
", x);
//        printf("%d < %d 
", siz[x], ask[i].k);
        if(siz[x] < ask[i].k) ans[ask[i].id] = -1;
        else ans[ask[i].id] = X[query(ask[i].k, 1, xx, rt[x])];
    }
    for(int i = 1; i <= q; i++) {
        printf("%d
", ans[i]);
    }
    return 0;
}