P2947 [USACO09MAR]向右看齐Look Up

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https://www.luogu.org/problemnew/show/P2947

题目描述
Farmer John's N (1 <= N <= 100,000) cows, conveniently numbered 1..N, are once again standing in a row. Cow i has height H_i (1 <= H_i <= 1,000,000).

Each cow is looking to her left toward those with higher index numbers. We say that cow i 'looks up' to cow j if i < j and H_i < H_j. For each cow i, FJ would like to know the index of the first cow in line looked up to by cow i.

Note: about 50% of the test data will have N <= 1,000.

约翰的N(1≤N≤10^5)头奶牛站成一排，奶牛i的身高是Hi(l≤Hi≤1,000,000)．现在，每只奶牛都在向右看齐．对于奶牛i，如果奶牛j满足i<j且Hi<Hj，我们可以说奶牛i可以仰望奶牛j． 求出每只奶牛离她最近的仰望对象．

Input

输入输出格式
输入格式：
* Line 1: A single integer: N

* Lines 2..N+1: Line i+1 contains the single integer: H_i

第 1 行输入 N，之后每行输入一个身高 H_i。

输出格式：
* Lines 1..N: Line i contains a single integer representing the smallest index of a cow up to which cow i looks. If no such cow exists, print 0.

共 N 行，按顺序每行输出一只奶牛的最近仰望对象，如果没有仰望对象，输出 0。

输入输出样例
输入样例#1：
6
3
2
6
1
1
2
输出样例#1：
3
3
0
6
6
0
说明
FJ has six cows of heights 3, 2, 6, 1, 1, and 2.

Cows 1 and 2 both look up to cow 3; cows 4 and 5 both look up to cow 6; and cows 3 and 6 do not look up to any cow.

【输入说明】6 头奶牛的身高分别为 3, 2, 6, 1, 1, 2.

【输出说明】奶牛#1,#2 仰望奶牛#3，奶牛#4,#5 仰望奶牛#6，奶牛#3 和#6 没有仰望对象。

【数据规模】

对于 20%的数据： 1≤N≤10；

对于 50%的数据： 1≤N≤1,000；

对于 100%的数据：1≤N≤100,000；1≤H_i≤1,000,000；

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1. program q3493;
   
2. var
   
3.   h,d1,d2,a:array[0..100000] of longint;
   
4.   n,i,j,k,tail:longint;
   
5. begin
   
6.   readln(n);
   
7.   for i:=1 to n do
   
8.     readln(h[i]);
   
9.   tail:=0;
   
10.   for i:=1 to n do
    
11.   begin
    
12.     while (tail>0) and (h[i]>d1[tail]) do
    
13.     begin
    
14.       a[d2[tail]]:=i;
    
15.       dec(tail);
    
16.     end;
    
17.     inc(tail);
    
18.     d1[tail]:=h[i];
    
19.     d2[tail]:=i;
    
20.   end;
    
21.   for i:=1 to n do
    
22.     writeln(a[i]);
    
23. end.

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