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  1. #include <iostream>
  2. using namespace std;
  3. #include<vector>
  4. #include <bits/stdc++.h>
  5.  
  6. int main() {
  7. 	// your code goes here
  8.     int n;
  9.     cin>>n;
  10.     vector<int>arr(n+1);
  11.     int i=1;
  12.     while(i<=n)
  13.      {
  14.      	cin>>arr[i];
  15.      	i++;
  16.      }
  17.  
  18.      int prefix[n+1]={0};
  19.  
  20.       prefix[0]=0;
  21.       int inc_len=0;
  22.       for(int i=1;i<=n;i++)
  23.        {
  24.        	 if(arr[i-1]<arr[i])
  25.        	  {
  26.        	  	prefix[i]=prefix[i-1]+1;
  27.        	  }
  28.        	  else
  29.        	   {
  30.        	   	prefix[i]=1;
  31.        	   }
  32.  
  33.        	   inc_len=max(inc_len,prefix[i]);
  34.        	   //cout<<prefix[i]<<'\n';
  35.  
  36.        }
  37.         //cout<<inc_len;
  38.  
  39.        int suffix[n+1];
  40.        suffix[n]=1;
  41.        int dec_len=0;
  42.        for(int i=n-1;i>=1;i--)
  43.         {
  44.         	if(arr[i]>arr[i+1])
  45.         	 {
  46.         	 	suffix[i]=suffix[i+1]+1;
  47.         	 }
  48.         	 else
  49.         	  {
  50.         	  	suffix[i]=1;
  51.         	  }
  52.         	 // cout<<suffix[i]<<'\n';
  53.         	  dec_len=max(dec_len,suffix[i]);
  54.         }
  55.  
  56.         //cout<<dec_len;
  57.  
  58.  
  59.         // largest mountain:
  60.  
  61.         //cout<<(inc_len+dec_len-1);
  62.  
  63.         //no of mountains whose topmost index is 'i'
  64.  
  65.         int count_mountains=0;
  66.         for(int i=1;i<=n;i++)
  67.          {
  68.          	if(prefix[i]>=2&&suffix[i]>=2)
  69.          	count_mountains+=(prefix[i]-1)*(suffix[i]-1);
  70.          }
  71.  
  72.          cout<<count_mountains;
  73.  
  74.  
  75.  
  76.  
  77.  
  78.  
  79. 	return 0;
  80. }
Success #stdin #stdout 0.01s 5300KB
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https://ideone.com/ZjDATn
language:
C++ (gcc 8.3)
created:
16 days ago
visibility:
public

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