hdu 2795 线段树

因为最多只有200000个点，每个海报的高度都是1单位，所以可能被用到的高度就是min(h,n)，然后记录每个点高度，利用线段树维护区间最大值，然后利用二分思想每次找到最靠上的广告位置，然后修改当前行的值．

#include <cstring>
#include <cstdio>
#include <algorithm>
#include <iostream>
#define MAX 200007

using namespace std;

int h,w,n;

struct Node
{
    int l,r,maxn;
}tree[MAX<<2];

void push_up ( int u )
{
    tree[u].maxn = max ( tree[u<<1].maxn , tree[u<<1|1].maxn );
}

void build ( int u , int l , int r )
{
    tree[u].l = l , tree[u].r = r;
    tree[u].maxn = w;
    if ( l == r ) return;
    int mid = l + r >> 1;
    build ( u<<1 , l , mid );
    build ( u<<1|1 , mid+1 , r ); 
}

void update ( int u , int x , int v )
{
    int l = tree[u].l , r = tree[u].r;
    if ( l == r )
    {
        tree[u].maxn -= v;
        return;
    }
    int mid = l + r >> 1;
    if ( x > mid ) update ( u<<1|1 , x , v );
    else update ( u<<1 , x , v );
    push_up ( u );
}

int x;

void find ( int u , int v )
{
    int l = tree[u].l , r = tree[u].r;
    if ( l == r ) 
    {
        x = l;
        return;
    }
    if ( v > tree[u].maxn ) return;
    if ( v > tree[u<<1].maxn ) find ( u<<1|1 , v );
    else find ( u<<1 , v );
}

int main ( )
{
    int a;
    while ( ~scanf ( "%d%d%d" , &h, &w, &n ) )
    {
        build ( 1 , 1 , min ( h , n+1 ) );
        for ( int i = 0 ; i < n ; i++ )
        {
            scanf ( "%d" , &a );
            x = -1;
            find ( 1 , a );
            printf ( "%d\n" , x );
            if ( x != -1 ) update ( 1 , x , a );
        }
    }   
}