HDU 5532 almost Sorted Array (longest not descending or not ascending sub-sequence)

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title: give you a sequence that asks you, this sequence decreases only one element, decreases afterwards whether it is not ascending or not descending sequence.

train of thought: directly to the sequence to find the longest non-descending and non-ascending sub-sequence, if the length of the sub-sequence is n-1 or N, it will meet the problem conditions.

Longest non- descending subsequence and longest not ascending subsequence: Here the method of data structure is used to find the length of the longest non-ascending (descending) sub-sequence. is to construct an array f[], this array means: f [i] represents the minimum (maximum) of a subsequence of length I, because, the same length of the sub-sequence, the last number is the smallest or largest, more convenient to put the number behind. This time may say that even if my number is small enough or large enough, if the position is not correct, then the length of the sequence ending with him cannot be the longest. As for this question, in fact, we update is f[], every time we all sweep f[], update this array, there will be no problem.

1#include <stdio.h>2#include <iostream>3#include <string.h>4#include <math.h>5#include <algorithm>6#include <vector>7#include <string>8#include <queue>9#include <map>Ten#include <stack> One#include <Set> A #definell Long Long - #defineMAXN 100010 - #definePI ACOs (-1.0)//Pi the Const intmod=1e9+7; - using namespacestd; - intNUM[MAXN]; - intF[MAXN]; + intN; - intMain () + { A     intT; atscanf"%d",&T); -      while(t--) -     { -Memset (F,0,sizeof(f)); -memset (NUM,0,sizeof(num)); -  inscanf"%d",&n); -          for(intI=0; i<n;i++) scanf ("%d",&num[i]); to  +         intlen=1; -f[0]=num[0]; the          for(intI=1; i<n;i++) *         { $             if(num[i]>=f[len-1]) f[len++]=Num[i];Panax Notoginseng             Else -             { the                 intCnt=upper_bound (F,f+len,num[i])-F; +f[cnt]=Num[i]; A             } the         } +  -         if(len==n-1|| len==N) $         { $printf"yes\n"); -             Continue; -         } the  -len=1;WuyiMemset (F,0,sizeof(f)); thef[0]=num[n-1]; -          for(inti=n-2; i>=0; i--) Wu         { -             if(num[i]>=f[len-1]) f[len++]=Num[i]; About             Else $             { -                 intCnt=upper_bound (F,f+len,num[i])-F; -f[cnt]=Num[i]; -             } A         } +  the         if(len==n-1|| Len==n) printf ("yes\n"); -         Elseprintf"no\n"); $     } the  the     return 0; the}

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HDU 5532 almost Sorted Array (longest not descending or not ascending sub-sequence)