1. 程式人生 > >Buy Tickets(線段樹單點更新,逆向思維)

Buy Tickets(線段樹單點更新,逆向思維)

fin eve lang sum free orz cst ssi -s

題目大意:有n個的排隊,每一個人都有一個val來對應,每一個後來人都會插入當前隊伍的某一個位置pos。要求把隊伍最後的狀態輸出。

個人心得:哈哈,用鏈表寫了下,果不其然超時了,後面轉念一想要用靜態數組思維, 還是炸了。大牛們很給力,逆向一轉,真是服氣。

一想是呀,轉過來的話那麽此時的人必然可以得到他的位置,此時更新長度,後面的人在此時的隊列中依舊可以得到他想要的位置。

就算思路知道了,怎麽實現呢,大神果然不愧是大神,線段樹sum表示總長度,節點表示是否存在被占據,然後更新就可以了。

真的是佩服到一派塗地,orz.....orz

題目原文:

Railway tickets were difficult to buy around the Lunar New Year in China, so we must get up early and join a long queue…

The Lunar New Year was approaching, but unluckily the Little Cat still had schedules going here and there. Now, he had to travel by train to Mianyang, Sichuan Province for the winter camp selection of the national team of Olympiad in Informatics.

It was one o’clock a.m. and dark outside. Chill wind from the northwest did not scare off the people in the queue. The cold night gave the Little Cat a shiver. Why not find a problem to think about? That was none the less better than freezing to death!

People kept jumping the queue. Since it was too dark around, such moves would not be discovered even by the people adjacent to the queue-jumpers. “If every person in the queue is assigned an integral value and all the information about those who have jumped the queue and where they stand after queue-jumping is given, can I find out the final order of people in the queue?” Thought the Little Cat.

Input

There will be several test cases in the input. Each test case consists of N + 1 lines where N (1 ≤ N ≤ 200,000) is given in the first line of the test case. The next N lines contain the pairs of values Posi and Vali in the increasing order of i(1 ≤ iN). For each i, the ranges and meanings of Posi and Vali are as follows:

  • Posi ∈ [0, i ? 1] — The i-th person came to the queue and stood right behind the Posi-th person in the queue. The booking office was considered the 0th person and the person at the front of the queue was considered the first person in the queue.
  • Vali ∈ [0, 32767] — The i-th person was assigned the value Vali.

There no blank lines between test cases. Proceed to the end of input.

Output

For each test cases, output a single line of space-separated integers which are the values of people in the order they stand in the queue.

Sample Input

4
0 77
1 51
1 33
2 69
4
0 20523
1 19243
1 3890
0 31492

Sample Output

77 33 69 51
31492 20523 3890 19243

Hint

The figure below shows how the Little Cat found out the final order of people in the queue described in the first test case of the sample input.

技術分享圖片
 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cmath>
 4 #include<cstring>
 5 #include<iomanip>
 6 #include<algorithm>
 7 using namespace std;
 8 #define inf 1<<29
 9 #define nu 4000005
10 #define maxnum 200005
11 int n;
12 int ans[maxnum],sum[maxnum<<2];
13 int pre[maxnum],val[maxnum];
14 void upset(int root)
15 {
16     sum[root]=sum[root*2]+sum[root*2+1];
17 }
18 void build(int root,int l,int r)
19 {
20     if(l==r)
21     {
22         sum[root]=1;
23         return ;
24     }
25     int mid=(l+r)/2;
26     build(root*2,l,mid);
27     build(root*2+1,mid+1,r);
28     upset(root);
29 }
30 void update(int root,int l,int r,int j)
31 {
32     if(l==r){
33         sum[root]--;
34         ans[l]=val[j];
35         return ;
36     }
37     int mid=(l+r)/2;
38     if(sum[root*2]>=pre[j])
39         update(root*2,l,mid,j);
40     else
41     {
42        pre[j]-=sum[root*2];
43        update(root*2+1,mid+1,r,j);
44     }
45     upset(root);
46 }
47 int main()
48 {
49     int i,j;
50     while(scanf("%d",&n)!=EOF){
51     for(i=1;i<=n;i++)
52         {
53            scanf("%d%d",&pre[i],&val[i]);
54             pre[i]++;
55         }
56     build(1,1,n);
57     for(i=n;i>0;i--)
58     {
59         update(1,1,n,i);
60     }
61    printf("%d",ans[1]);
62     for(i=2;i<=n;i++)
63        printf(" %d",ans[i]);
64        printf("\n");
65     }
66     return 0;
67 }

Buy Tickets(線段樹單點更新,逆向思維)