Subsecuencia bitónica más larga | DP-15 – Part 1

Dada una array arr[0 … n-1] que contiene n enteros positivos, una subsecuencia de arr[] se llama bitónica si primero es creciente y luego decreciente. Escriba una función que tome una array como argumento y devuelva la longitud de la subsecuencia bitónica más larga. 
Una secuencia ordenada en orden creciente se considera bitónica con la parte decreciente vacía. De manera similar, la secuencia de orden decreciente se considera bitónica con la parte creciente como vacía. 
Ejemplos:

Input arr[] = {1, 11, 2, 10, 4, 5, 2, 1};
Output: 6 (A Longest Bitonic Subsequence of length 6 is 1, 2, 10, 4, 2, 1)

Input arr[] = {12, 11, 40, 5, 3, 1}
Output: 5 (A Longest Bitonic Subsequence of length 5 is 12, 11, 5, 3, 1)

Input arr[] = {80, 60, 30, 40, 20, 10}
Output: 5 (A Longest Bitonic Subsequence of length 5 is 80, 60, 30, 20, 10)

Fuente: pregunta de la entrevista de Microsoft
 

C++

/* Dynamic Programming implementation of longest bitonic subsequence problem */
#include<stdio.h>
#include<stdlib.h>
  
/* lbs() returns the length of the Longest Bitonic Subsequence in
    arr[] of size n. The function mainly creates two temporary arrays
    lis[] and lds[] and returns the maximum lis[i] + lds[i] - 1.
  
    lis[i] ==> Longest Increasing subsequence ending with arr[i]
    lds[i] ==> Longest decreasing subsequence starting with arr[i]
*/
int lbs( int arr[], int n )
{
   int i, j;
  
   /* Allocate memory for LIS[] and initialize LIS values as 1 for
      all indexes */
   int *lis = new int[n];
   for (i = 0; i < n; i++)
      lis[i] = 1;
  
   /* Compute LIS values from left to right */
   for (i = 1; i < n; i++)
      for (j = 0; j < i; j++)
         if (arr[i] > arr[j] && lis[i] < lis[j] + 1)
            lis[i] = lis[j] + 1;
  
   /* Allocate memory for lds and initialize LDS values for
      all indexes */
   int *lds = new int [n];
   for (i = 0; i < n; i++)
      lds[i] = 1;
  
   /* Compute LDS values from right to left */
   for (i = n-2; i >= 0; i--)
      for (j = n-1; j > i; j--)
         if (arr[i] > arr[j] && lds[i] < lds[j] + 1)
            lds[i] = lds[j] + 1;
  
  
   /* Return the maximum value of lis[i] + lds[i] - 1*/
   int max = lis[0] + lds[0] - 1;
   for (i = 1; i < n; i++)
     if (lis[i] + lds[i] - 1 > max)
         max = lis[i] + lds[i] - 1;
   return max;
}
  
/* Driver program to test above function */
int main()
{
  int arr[] = {0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5,
              13, 3, 11, 7, 15};
  int n = sizeof(arr)/sizeof(arr[0]);
  printf("Length of LBS is %d\n", lbs( arr, n ) );
  return 0;
}

Java

/* Dynamic Programming implementation in Java for longest bitonic
   subsequence problem */
import java.util.*;
import java.lang.*;
import java.io.*;
  
class LBS
{
    /* lbs() returns the length of the Longest Bitonic Subsequence in
    arr[] of size n. The function mainly creates two temporary arrays
    lis[] and lds[] and returns the maximum lis[i] + lds[i] - 1.
  
    lis[i] ==> Longest Increasing subsequence ending with arr[i]
    lds[i] ==> Longest decreasing subsequence starting with arr[i]
    */
    static int lbs( int arr[], int n )
    {
        int i, j;
  
        /* Allocate memory for LIS[] and initialize LIS values as 1 for
            all indexes */
        int[] lis = new int[n];
        for (i = 0; i < n; i++)
            lis[i] = 1;
  
        /* Compute LIS values from left to right */
        for (i = 1; i < n; i++)
            for (j = 0; j < i; j++)
                if (arr[i] > arr[j] && lis[i] < lis[j] + 1)
                    lis[i] = lis[j] + 1;
  
        /* Allocate memory for lds and initialize LDS values for
            all indexes */
        int[] lds = new int [n];
        for (i = 0; i < n; i++)
            lds[i] = 1;
  
        /* Compute LDS values from right to left */
        for (i = n-2; i >= 0; i--)
            for (j = n-1; j > i; j--)
                if (arr[i] > arr[j] && lds[i] < lds[j] + 1)
                    lds[i] = lds[j] + 1;
  
  
        /* Return the maximum value of lis[i] + lds[i] - 1*/
        int max = lis[0] + lds[0] - 1;
        for (i = 1; i < n; i++)
            if (lis[i] + lds[i] - 1 > max)
                max = lis[i] + lds[i] - 1;
  
        return max;
    }
  
    public static void main (String[] args)
    {
        int arr[] = {0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5,
                    13, 3, 11, 7, 15};
        int n = arr.length;
        System.out.println("Length of LBS is "+ lbs( arr, n ));
    }
}

Python3

# Dynamic Programming implementation of longest bitonic subsequence problem
"""
lbs() returns the length of the Longest Bitonic Subsequence in
arr[] of size n. The function mainly creates two temporary arrays
lis[] and lds[] and returns the maximum lis[i] + lds[i] - 1.
  
lis[i] ==> Longest Increasing subsequence ending with arr[i]
lds[i] ==> Longest decreasing subsequence starting with arr[i]
"""
  
def lbs(arr):
    n = len(arr)
  
  
    # allocate memory for LIS[] and initialize LIS values as 1
    # for all indexes
    lis = [1 for i in range(n+1)]
  
    # Compute LIS values from left to right
    for i in range(1 , n):
        for j in range(0 , i):
            if ((arr[i] > arr[j]) and (lis[i] < lis[j] +1)):
                lis[i] = lis[j] + 1
  
    # allocate memory for LDS and initialize LDS values for
    # all indexes
    lds = [1 for i in range(n+1)]
      
    # Compute LDS values from right to left
    for i in reversed(range(n-1)): #loop from n-2 downto 0
        for j in reversed(range(i-1 ,n)): #loop from n-1 downto i-1
            if(arr[i] > arr[j] and lds[i] < lds[j] + 1):
                lds[i] = lds[j] + 1 
  
  
    # Return the maximum value of (lis[i] + lds[i] - 1)
    maximum = lis[0] + lds[0] - 1
    for i in range(1 , n):
        maximum = max((lis[i] + lds[i]-1), maximum)
      
    return maximum
  
# Driver program to test the above function
arr =  [0 , 8 , 4, 12, 2, 10 , 6 , 14 , 1 , 9 , 5 , 13,
        3, 11 , 7 , 15]
print ("Length of LBS is",lbs(arr))
  
# This code is contributed by Nikhil Kumar Singh(nickzuck_007)

C#

/* Dynamic Programming implementation in 
   C# for longest bitonic subsequence problem */
using System;
  
class LBS {
      
    /* lbs() returns the length of the Longest Bitonic Subsequence in
    arr[] of size n. The function mainly creates two temporary arrays
    lis[] and lds[] and returns the maximum lis[i] + lds[i] - 1.
  
    lis[i] ==> Longest Increasing subsequence ending with arr[i]
    lds[i] ==> Longest decreasing subsequence starting with arr[i]
    */
    static int lbs(int[] arr, int n)
    {
        int i, j;
  
        /* Allocate memory for LIS[] and initialize 
           LIS values as 1 for all indexes */
        int[] lis = new int[n];
        for (i = 0; i < n; i++)
            lis[i] = 1;
  
        /* Compute LIS values from left to right */
        for (i = 1; i < n; i++)
            for (j = 0; j < i; j++)
                if (arr[i] > arr[j] && lis[i] < lis[j] + 1)
                    lis[i] = lis[j] + 1;
  
        /* Allocate memory for lds and initialize LDS values for
            all indexes */
        int[] lds = new int[n];
        for (i = 0; i < n; i++)
            lds[i] = 1;
  
        /* Compute LDS values from right to left */
        for (i = n - 2; i >= 0; i--)
            for (j = n - 1; j > i; j--)
                if (arr[i] > arr[j] && lds[i] < lds[j] + 1)
                    lds[i] = lds[j] + 1;
  
        /* Return the maximum value of lis[i] + lds[i] - 1*/
        int max = lis[0] + lds[0] - 1;
        for (i = 1; i < n; i++)
            if (lis[i] + lds[i] - 1 > max)
                max = lis[i] + lds[i] - 1;
  
        return max;
    }
      
    // Driver code
    public static void Main()
    {
        int[] arr = { 0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5,
                                      13, 3, 11, 7, 15 };
        int n = arr.Length;
        Console.WriteLine("Length of LBS is " + lbs(arr, n));
    }
}
  
// This code is contributed by vt_m.

PHP

<?php 
// Dynamic Programming implementation
// of longest bitonic subsequence problem 
  
/* lbs() returns the length of the Longest 
   Bitonic Subsequence in arr[] of size n. 
   The function mainly creates two temporary 
   arrays lis[] and lds[] and returns the 
   maximum lis[i] + lds[i] - 1.
  
   lis[i] ==> Longest Increasing subsequence
              ending with arr[i]
   lds[i] ==> Longest decreasing subsequence 
              starting with arr[i]
*/
function lbs(&$arr, $n)
{
  
    /* Allocate memory for LIS[] and initialize 
       LIS values as 1 for all indexes */
    $lis = array_fill(0, $n, NULL);
    for ($i = 0; $i < $n; $i++)
        $lis[$i] = 1;
      
    /* Compute LIS values from left to right */
    for ($i = 1; $i < $n; $i++)
        for ($j = 0; $j < $i; $j++)
            if ($arr[$i] > $arr[$j] && 
                $lis[$i] < $lis[$j] + 1)
                $lis[$i] = $lis[$j] + 1;
      
    /* Allocate memory for lds and initialize 
       LDS values for all indexes */
    $lds = array_fill(0, $n, NULL);
    for ($i = 0; $i < $n; $i++)
        $lds[$i] = 1;
      
    /* Compute LDS values from right to left */
    for ($i = $n - 2; $i >= 0; $i--)
        for ($j = $n - 1; $j > $i; $j--)
            if ($arr[$i] > $arr[$j] && 
                $lds[$i] < $lds[$j] + 1)
                $lds[$i] = $lds[$j] + 1;
      
    /* Return the maximum value of 
       lis[i] + lds[i] - 1*/
    $max = $lis[0] + $lds[0] - 1;
    for ($i = 1; $i < $n; $i++)
        if ($lis[$i] + $lds[$i] - 1 > $max)
            $max = $lis[$i] + $lds[$i] - 1;
    return $max;
}
  
// Driver Code
$arr = array(0, 8, 4, 12, 2, 10, 6, 14, 
             1, 9, 5, 13, 3, 11, 7, 15);
$n = sizeof($arr);
echo "Length of LBS is " . lbs( $arr, $n );
  
// This code is contributed by ita_c
?>

Javascript

<script>
  
/* Dynamic Programming implementation in JavaScript for longest bitonic 
   subsequence problem */    
      
    /* lbs() returns the length of the Longest Bitonic Subsequence in 
    arr[] of size n. The function mainly creates two temporary arrays 
    lis[] and lds[] and returns the maximum lis[i] + lds[i] - 1. 
    
    lis[i] ==> Longest Increasing subsequence ending with arr[i] 
    lds[i] ==> Longest decreasing subsequence starting with arr[i] 
    */
    function lbs(arr,n)
    {
        let i, j; 
        /* Allocate memory for LIS[] and initialize LIS values as 1 for 
            all indexes */
        let lis = new Array(n)
        for (i = 0; i < n; i++) 
            lis[i] = 1;
          
        /* Compute LIS values from left to right */
        for (i = 1; i < n; i++) 
            for (j = 0; j < i; j++) 
                if (arr[i] > arr[j] && lis[i] < lis[j] + 1) 
                    lis[i] = lis[j] + 1; 
    
        /* Allocate memory for lds and initialize LDS values for 
            all indexes */
        let lds = new Array(n); 
        for (i = 0; i < n; i++) 
            lds[i] = 1; 
    
        /* Compute LDS values from right to left */
        for (i = n-2; i >= 0; i--) 
            for (j = n-1; j > i; j--) 
                if (arr[i] > arr[j] && lds[i] < lds[j] + 1) 
                    lds[i] = lds[j] + 1; 
    
    
        /* Return the maximum value of lis[i] + lds[i] - 1*/
        let max = lis[0] + lds[0] - 1; 
        for (i = 1; i < n; i++) 
            if (lis[i] + lds[i] - 1 > max) 
                max = lis[i] + lds[i] - 1; 
    
        return max; 
    }
    let arr=[0, 8, 4, 12, 2, 10, 6, 14, 1, 9, 5, 13, 3, 11, 7, 15]
    let n = arr.length;
    document.write("Length of LBS is "+ lbs( arr, n )); 
          
    // This code is contributed by avanitrachhadiya2155
      
</script>

Publicación traducida automáticamente

Artículo escrito por GeeksforGeeks-1 y traducido por Barcelona Geeks. The original can be accessed here. Licence: CCBY-SA

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