hdu 5493 Queue（线段树）

题目链接：hdu 5493 Queue

解题思路

将人头按照从小到大排序，每次优先放小的，尽量靠前。
用线段树维护空位，每次判断前隔k人靠前还是后隔k人靠前。

代码

#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>

using namespace std;
const int maxn = 100005;
typedef pair<int,int> pii;
#define lson(x) ((x)<<1)
#define rson(x) (((x)<<1)|1)

struct SegTree {
    int lc[maxn<<2], rc[maxn<<2], s[maxn<<2];

    void pushup(int u) { s[u] = s[lson(u)] + s[rson(u)]; }

    void build (int u, int l, int r) {
        lc[u] = l, rc[u] = r, s[u] = 1;

        if (l == r) return;

        int mid = (l + r) >> 1;
        build(lson(u), l, mid);
        build(rson(u), mid+1, r);
        pushup(u);
    }

    void modify(int u, int x) {
        if (lc[u] == rc[u]) {
            s[u] = 0;
            return;
        }

        int mid = (lc[u] + rc[u])>>1;
        if (x <= mid) modify(lson(u), x);
        else modify(rson(u), x);
        pushup(u);
    }

    int query(int u, int x) {
        if (lc[u] == rc[u])
            return lc[u];

        int mid = (lc[u] + rc[u])>>1;
        if (s[lson(u)] >= x) return query(lson(u), x);
        else return query(rson(u), x - s[lson(u)]);
    }
}T;

int N, A[maxn];
vector<pii> G;

void init () {
    int h, k;
    scanf("%d", &N);

    G.clear();
    for (int i = 1; i <= N; i++) {
        scanf("%d%d", &h, &k);
        G.push_back(make_pair(h, k));
    }
    sort(G.begin(), G.end());

    T.build(1, 1, N);
}

bool solve () {

    for (int i = 0; i < N; i++) {
        if (G[i].second >= N-i) return false;
        int pre = G[i].second + 1, suf = N-i-G[i].second;
        int pos = min(T.query(1, pre), T.query(1, suf));
        A[pos] = G[i].first;
        T.modify(1, pos);
    }

    for (int i = 1; i <= N; i++)
        printf(" %d", A[i]);
    printf("\n");
    return true;
}

int main () {
    int cas;
    scanf("%d", &cas);
    for (int kcas = 1; kcas <= cas; kcas++) {
        init();
        printf("Case #%d:", kcas);
        if (!solve()) printf(" impossible\n");
    }
    return 0;
}