At the entrance to the university, there is a huge rectangular billboard of size h*w (h is its height and w is its width). The board is the place where all possible announcements are posted: nearest programming competitions, changes
in the dining room menu, and other important information.
On September 1, the billboard was empty. One by one, the announcements started being put on the billboard.
Each announcement is a stripe of paper of unit height. More specifically, the i-th announcement is a rectangle of size 1 * wi.
When someone puts a new announcement on the billboard, she would always choose the topmost possible position for the announcement. Among all possible topmost positions she would always choose the leftmost one.
If there is no valid location for a new announcement, it is not put on the billboard (that's why some programming contests have no participants from this university).
Given the sizes of the billboard and the announcements, your task is to find the numbers of rows in which the announcements are placed.
On September 1, the billboard was empty. One by one, the announcements started being put on the billboard.
Each announcement is a stripe of paper of unit height. More specifically, the i-th announcement is a rectangle of size 1 * wi.
When someone puts a new announcement on the billboard, she would always choose the topmost possible position for the announcement. Among all possible topmost positions she would always choose the leftmost one.
If there is no valid location for a new announcement, it is not put on the billboard (that's why some programming contests have no participants from this university).
Given the sizes of the billboard and the announcements, your task is to find the numbers of rows in which the announcements are placed.
The first line of the input file contains three integer numbers, h, w, and n (1 <= h,w <= 10^9; 1 <= n <= 200,000) - the dimensions of the billboard and the number of announcements.
Each of the next n lines contains an integer number wi (1 <= wi <= 10^9) - the width of i-th announcement.
3 5 5 2 4 3 3 3
1 2 1 3 -1
题目大意:一个h*w的公告牌,要在其上贴公告。输入的是1*wi的w值,这些是公告的尺寸接下来要满足的条件有:1、尽量往上,同一高度尽量靠左。2、求第n个广告所在的行数。3、没有合适的位置贴了则输出-1。
解题思路:用max1数组来表示这段区间内有最多空位的那一行的空位长度。与输入进来的长度进行比较,先左边比较,再右边。(也就是左子树的最大值大于他,就查询左子树,否则查询右子树)。
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#define N 200002
using namespace std;
int w,max1[N<<2];//表示某个节点的区间空余的最大长度,max1[1]即所有区间的最大空余长度(初始为w)
void creat(int rf,int l,int r)
{
if(l==r)
{
max1[rf]=w;
return ;
}
int mid=(l+r)>>1;
creat(2*rf,l,mid);
creat(2*rf+1,mid+1,r);
max1[rf]=max(max1[2*rf],max1[2*rf+1]);
}
int update(int a,int l,int r,int rf)
{
if(l==r)
{
max1[rf]-=a;
return l;
}
int mid=(l+r)>>1;
int ans;
if(max1[rf*2]>=a)
ans=update(a,l,mid,rf*2);
else if(max1[rf*2+1]>=a)
ans=update(a,mid+1,r,rf*2+1);
max1[rf]=max(max1[rf*2],max1[rf*2+1]);
return ans;
}
int main()
{
int h,n,a;
while(~scanf("%d%d%d",&h,&w,&n))
{
int min1=min(n,h);
creat(1,1,min1);
while(n--)
{
scanf("%d",&a);
if(a<=max1[1])
printf("%d\n",update(a,1,min1,1));
else
printf("-1\n");
}
}
return 0;
}
本文介绍了一个高效的算法,用于解决在限定大小的公告牌上按特定规则张贴不同宽度公告的问题。该算法利用了区间树的数据结构,能够快速找到并更新公告在公告牌上的位置。
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