POJ 2828 Buy Tickets 线段树

Buy Tickets
Time Limit: 4000MS   Memory Limit: 65536K
Total Submissions: 16592   Accepted: 8271

Description

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 ≤ i ≤ N). For each i, the ranges and meanings of Posi and Vali are as follows:(注意红色的字,漏看了这一句话,折磨了好几天。。。)

  • 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.

POJ 2828 Buy Tickets 线段树_第1张图片

Source

POJ Monthly--2006.05.28, Zhu, Zeyuan


思路各个大牛都说的很清楚,逆序插入,相比较正序插入,每个成员的位置都不会在变化,所以只需要检测每次的空位进行插入就好。重点说说上面加红的那句话,如果题目没有这句话,那么这种做法就是错误的!([捂脸],自己提出了一个序列,结果看了超级多的题目讲解,始终不明白这个序列输出的为什么不对,好好看题很重要啊!!!)

假设这个序列前面没有按序给出。
例:6
2 88
1 77
0 66
0 55
0 44
0 33

那么本来的排列是:33,44,55,66,77,88
但是逆序按照程序插入,结果就是错的:33,44,55,66,(空),88
即77也会在6位置上,但是后来又被88覆盖了
类似的,如果前面给出的序列是倒序的话,那么这种做法就是错误的。
写在这里,请和我一样马虎的朋友们少废点功夫……
#include<stdio.h>
#define MAX_N 200001
#define lson l,m,level*2
#define rson m+1,r,level*2+1
typedef struct{
	int pos;
	int val;
}person;
int N;
person a[MAX_N];   //录入的数据
int tree[MAX_N*4];  //线段树
int result[MAX_N];  //最终队列的顺序


void insert(int l,int r,int level,int x,int value){
	tree[level]--;              //进入这一段,空的位置就减一
	if(l == r){
		result[l] = value;
		return ;
	}
	int m = (l + r)/2;
	if(x<=tree[level*2]){
		insert(lson,x,value);
	}
	else{
		insert(rson,x-tree[level*2],value);           //若进入右子树,则排列的位置减去前面的空的位置
	}
	
}

void build(int l,int r,int level){
	tree[level] = r - l + 1;
	if(l == r){
		return ;
	}
	int m = (l + r)/2;
	build(lson);
	build(rson);
}

int main(){
	while(scanf("%d",&N)!=EOF){
		for(int i=0;i<N;i++){
			scanf("%d%d",&a[i].pos,&a[i].val);
		}
		build(1,N,1);
		for(int i=N-1;i>=0;i--){
			insert(1,N,1,a[i].pos+1,a[i].val);
		}
		for(int i=1;i<N;i++){
			printf("%d ",result[i]);
		}
		printf("%d\n",result[N]);
		
	}
	
	return 0;
} 



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