学步园

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=3577

代码风格：http://www.notonlysuccess.com/index.php/segment-tree-complete/

题目大意：买火车票问题，一辆火车最多有1000000个站点，站点最多能容下Q个人，一共有k个乘客

每个乘客需要从第a站坐到第b站，所以要保证火车到任何站台，人数都不会超过Q个人，让我看输出哪几个乘客能上车

算法：线段树 离散化

思路：求[a, b]区间的最小值是不是为零

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;

#define lson l, m, rt << 1
#define rson m+1, r, rt << 1 | 1
#define mid int m = (l+r) >> 1

int mn[4000000], cover[4000000], w[454545], ri[223232], li[232323];

void build(int l, int r, int rt, int k)
{
    mn[rt] = k;
    if(l == r)
        return ;
    mid ;
    build(lson, k);
    build(rson, k);
}

int minz(int a, int b)
{
    return a < b ? a : b;
}

void PushUp(int rt)
{
    mn[rt] = minz(mn[rt << 1], mn[rt << 1 | 1]);
}

void PushDown(int rt)
{
    cover[rt << 1] += cover[rt];
    cover[rt << 1 | 1] += cover[rt];
    mn[rt << 1] -= cover[rt];
    mn[rt << 1 | 1] -= cover[rt];
    cover[rt] = 0;
}

void update(int L, int R, int l, int r, int rt)
{
    if(L <= l && r <= R)
    {
        cover[rt] ++;
        mn[rt] --;
        return ;
    }
    mid ;
    cover[rt << 1] += cover[rt];
    cover[rt << 1 | 1] += cover[rt];
    mn[rt << 1] -= cover[rt];
    mn[rt << 1 | 1] -= cover[rt];
    cover[rt] = 0;
    if(L <= m)
        update(L, R, lson);
    if(m < R)
        update(L, R, rson);
    mn[rt] = minz(mn[rt << 1], mn[rt << 1 | 1]);
}

int query(int L, int R, int l, int r, int rt)
{
    if(L <= l && r <= R)
    {
        if(mn[rt] != 0)
            return 1;
        else
            return 0;
    }
    mid ;
    cover[rt << 1] += cover[rt];
    cover[rt << 1 | 1] += cover[rt];
    mn[rt << 1] -= cover[rt];
    mn[rt << 1 | 1] -= cover[rt];
    cover[rt] = 0;
    int ret1=1, ret2=1;
    if(L <= m)
        ret1 = query(L, R, lson);
    if(m < R)
        ret2 = query(L, R, rson);
    return ret1 & ret2;
}

int bin(int key, int n)
{
    int l = 0, r = n;
    while(l <= r)
    {
        mid ;
        if(w[m] == key)
            return m;
        if(key < w[m])
            r = m - 1;
        else
            l = m+1;
    }
    return -1;
}

int main()
{
    int n, m;
    int T;
    scanf("%d", &T);
    int ica = 1;
    while(T --)
    {
        printf("Case %d:\n", ica ++);
        memset(cover, 0, sizeof(cover));
        int i;
        int maxn = 0;
        scanf("%d%d", &n, &m);
        int k = 0;
        for(i = 1; i <= m; i ++)
        {
            scanf("%d%d", &li[i], &ri[i]);
            w[k ++] = li[i];
            w[k ++] = ri[i];
        }
        sort(w, w+k);
        int u = 1;
        for(i = 1; i < k; i ++)
            if(w[i] != w[i-1])
                w[u ++] = w[i];
        build(0, u-1, 1, n);
        for(i = 1; i <= m; i ++)
        {
            int ll = bin(li[i], u-1 );
            int rr = bin(ri[i], u-1 )-1;
            int flag = query(ll, rr, 0, u-2, 1);
            if(flag && ll <= rr)
            {
                update(ll, rr, 0, u-2, 1);
                printf("%d ", i);
            }
        }
        printf("\n\n");
    }return 0;
}