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Raskite, ar pogrupis yra kalno formos, ar ne

Išbandykite GfG praktikoje ' title= #practiceLinkDiv { display: none !important; }

Mums duotas sveikųjų skaičių masyvas ir diapazonas, kurio reikia, kad sužinotume, ar į šį diapazoną patenkantis pogrupis turi reikšmes kalno pavidalu, ar ne. Sakoma, kad visos pogrupio reikšmės yra kalno formos, jei visos vertės didėja arba mažėja, arba iš pradžių didėja, o paskui mažėja. 
Formaliai subarray [a1 a2 a3…aN] Sakoma, kad jis yra kalno formos, jei yra sveikasis skaičius K 1<= K <= N such that 
a1<= a2 <= a3 .. <= aK >= a(K+1) >= a(K+2) …. >= aN  

Pavyzdžiai:  

  Input : Arr[]   = [2 3 2 4 4 6 3 2] Range = [0 2]   Output :    Yes   Explanation:   The output is yes  subarray is [2 3 2] so subarray first increases and then decreases   Input:    Arr[] = [2 3 2 4 4 6 3 2] Range = [2 7]   Output:   Yes   Explanation:   The output is yes  subarray is [2 4 4 6 3 2] so subarray first increases and then decreases   Input:   Arr[]= [2 3 2 4 4 6 3 2] Range = [1 3]   Output:   no   Explanation:   The output is no subarray is [3 2 4] so subarray is not in the form above stated
Recommended Practice Mountain Subarray problema Išbandykite!

Sprendimas:  



    Prieiga:Problema turi kelias užklausas, todėl kiekvienos užklausos sprendimas turėtų būti apskaičiuotas kuo mažiau sudėtingu laiku. Taigi sukurkite du papildomus pradinio masyvo ilgio tarpus. Kiekvieno elemento kairėje pusėje suraskite paskutinį indeksą, kuris didėja, t. y. didesnis už ankstesnį elementą, o dešinėje pusėje esantis elementas išsaugos pirmąjį indeksą dešinėje, kuris mažėja, t. y. didesnis už kitą elementą. Jei šias vertes galima apskaičiuoti kiekvienam indeksui pastoviu laiku, tai kiekvienam duotam diapazonui atsakymą galima pateikti pastoviu laiku.Algoritmas: 
    1. Sukurkite du papildomus ilgio tarpus n paliko ir teisingai ir papildomas kintamasis lastptr
    2. Inicijuoti paliko[0] = 0 ir lastptr = 0
    3. Pereikite pradinį masyvą nuo antrojo indekso iki pabaigos
    4. Kiekvienam indeksui patikrinkite, ar jis didesnis nei ankstesnis elementas, jei taip, tada atnaujinkite lastptr su dabartiniu indeksu.
    5. Kiekvienai indeksų saugyklai lastptr in paliko [i]
    6. inicijuoti dešinė[N-1] = N-1 ir lastptr = N-1
    7. Pereikite pradinį masyvą nuo antrojo paskutinio indekso iki pradžios
    8. Kiekvienam indeksui patikrinkite, ar jis didesnis už kitą elementą, jei taip, tada atnaujinkite lastptr su dabartiniu indeksu.
    9. Kiekvienai indeksų saugyklai lastptr in teisingai [i]
    10. Dabar apdorokite užklausas
    11. už kiekvieną užklausą l r jeigu dešinė[l] >= kairė[r] tada spausdinkite taip kitaip ne
    Įgyvendinimas:
C++
// C++ program to check whether a subarray is in // mountain form or not #include    using namespace std; // Utility method to construct left and right array int preprocess(int arr[] int N int left[] int right[]) {  // Initialize first left index as that index only  left[0] = 0;  int lastIncr = 0;  for (int i = 1; i < N; i++)  {  // if current value is greater than previous  // update last increasing  if (arr[i] > arr[i - 1])  lastIncr = i;  left[i] = lastIncr;  }  // Initialize last right index as that index only  right[N - 1] = N - 1;  int firstDecr = N - 1;  for (int i = N - 2; i >= 0; i--)  {  // if current value is greater than next  // update first decreasing  if (arr[i] > arr[i + 1])  firstDecr = i;  right[i] = firstDecr;  } } // Method returns true if arr[L..R] is in mountain form bool isSubarrayMountainForm(int arr[] int left[]  int right[] int L int R) {  // return true only if right at starting range is  // greater than left at ending range  return (right[L] >= left[R]); } // Driver code to test above methods int main() {  int arr[] = {2 3 2 4 4 6 3 2};  int N = sizeof(arr) / sizeof(int);  int left[N] right[N];  preprocess(arr N left right);  int L = 0;  int R = 2;  if (isSubarrayMountainForm(arr left right L R))  cout << 'Subarray is in mountain formn';  else  cout << 'Subarray is not in mountain formn';  L = 1;  R = 3;  if (isSubarrayMountainForm(arr left right L R))  cout << 'Subarray is in mountain formn';  else  cout << 'Subarray is not in mountain formn';  return 0; } 
Java
// Java program to check whether a subarray is in // mountain form or not class SubArray {  // Utility method to construct left and right array  static void preprocess(int arr[] int N int left[] int right[])  {  // initialize first left index as that index only  left[0] = 0;  int lastIncr = 0;    for (int i = 1; i < N; i++)  {  // if current value is greater than previous  // update last increasing  if (arr[i] > arr[i - 1])  lastIncr = i;  left[i] = lastIncr;  }    // initialize last right index as that index only  right[N - 1] = N - 1;  int firstDecr = N - 1;    for (int i = N - 2; i >= 0; i--)  {  // if current value is greater than next  // update first decreasing  if (arr[i] > arr[i + 1])  firstDecr = i;  right[i] = firstDecr;  }  }    // method returns true if arr[L..R] is in mountain form  static boolean isSubarrayMountainForm(int arr[] int left[]  int right[] int L int R)  {  // return true only if right at starting range is  // greater than left at ending range  return (right[L] >= left[R]);  }    public static void main(String[] args)  {  int arr[] = {2 3 2 4 4 6 3 2};  int N = arr.length;  int left[] = new int[N];  int right[] = new int[N];  preprocess(arr N left right);  int L = 0;  int R = 2;    if (isSubarrayMountainForm(arr left right L R))  System.out.println('Subarray is in mountain form');  else  System.out.println('Subarray is not in mountain form');    L = 1;  R = 3;    if (isSubarrayMountainForm(arr left right L R))  System.out.println('Subarray is in mountain form');  else  System.out.println('Subarray is not in mountain form');  } } // This Code is Contributed by Saket Kumar 
Python3
# Python 3 program to check whether a subarray is in # mountain form or not # Utility method to construct left and right array def preprocess(arr N left right): # initialize first left index as that index only left[0] = 0 lastIncr = 0 for i in range(1N): # if current value is greater than previous # update last increasing if (arr[i] > arr[i - 1]): lastIncr = i left[i] = lastIncr # initialize last right index as that index only right[N - 1] = N - 1 firstDecr = N - 1 i = N - 2 while(i >= 0): # if current value is greater than next # update first decreasing if (arr[i] > arr[i + 1]): firstDecr = i right[i] = firstDecr i -= 1 # method returns true if arr[L..R] is in mountain form def isSubarrayMountainForm(arr left right L R): # return true only if right at starting range is # greater than left at ending range return (right[L] >= left[R]) # Driver code  if __name__ == '__main__': arr = [2 3 2 4 4 6 3 2] N = len(arr) left = [0 for i in range(N)] right = [0 for i in range(N)] preprocess(arr N left right) L = 0 R = 2 if (isSubarrayMountainForm(arr left right L R)): print('Subarray is in mountain form') else: print('Subarray is not in mountain form') L = 1 R = 3 if (isSubarrayMountainForm(arr left right L R)): print('Subarray is in mountain form') else: print('Subarray is not in mountain form') # This code is contributed by # Surendra_Gangwar 
C#
// C# program to check whether  // a subarray is in mountain  // form or not using System; class GFG {    // Utility method to construct   // left and right array  static void preprocess(int []arr int N   int []left int []right)  {  // initialize first left   // index as that index only  left[0] = 0;  int lastIncr = 0;    for (int i = 1; i < N; i++)  {  // if current value is   // greater than previous  // update last increasing  if (arr[i] > arr[i - 1])  lastIncr = i;  left[i] = lastIncr;  }    // initialize last right   // index as that index only  right[N - 1] = N - 1;  int firstDecr = N - 1;    for (int i = N - 2; i >= 0; i--)  {  // if current value is   // greater than next  // update first decreasing  if (arr[i] > arr[i + 1])  firstDecr = i;  right[i] = firstDecr;  }  }    // method returns true if  // arr[L..R] is in mountain form  static bool isSubarrayMountainForm(int []arr int []left  int []right int L int R)  {  // return true only if right at   // starting range is greater   // than left at ending range  return (right[L] >= left[R]);  }      // Driver Code  static public void Main ()  {  int []arr = {2 3 2 4  4 6 3 2};  int N = arr.Length;  int []left = new int[N];  int []right = new int[N];  preprocess(arr N left right);    int L = 0;  int R = 2;    if (isSubarrayMountainForm(arr left   right L R))  Console.WriteLine('Subarray is in ' +   'mountain form');  else  Console.WriteLine('Subarray is not ' +   'in mountain form');    L = 1;  R = 3;    if (isSubarrayMountainForm(arr left   right L R))  Console.WriteLine('Subarray is in ' +   'mountain form');  else  Console.WriteLine('Subarray is not ' +   'in mountain form');  } } // This code is contributed by aj_36 
JavaScript
<script>  // Javascript program to check whether   // a subarray is in mountain   // form or not    // Utility method to construct   // left and right array  function preprocess(arr N left right)  {  // initialize first left   // index as that index only  left[0] = 0;  let lastIncr = 0;    for (let i = 1; i < N; i++)  {  // if current value is   // greater than previous  // update last increasing  if (arr[i] > arr[i - 1])  lastIncr = i;  left[i] = lastIncr;  }    // initialize last right   // index as that index only  right[N - 1] = N - 1;  let firstDecr = N - 1;    for (let i = N - 2; i >= 0; i--)  {  // if current value is   // greater than next  // update first decreasing  if (arr[i] > arr[i + 1])  firstDecr = i;  right[i] = firstDecr;  }  }    // method returns true if  // arr[L..R] is in mountain form  function isSubarrayMountainForm(arr left right L R)  {  // return true only if right at   // starting range is greater   // than left at ending range  return (right[L] >= left[R]);  }    let arr = [2 3 2 4 4 6 3 2];  let N = arr.length;  let left = new Array(N);  let right = new Array(N);  preprocess(arr N left right);  let L = 0;  let R = 2;  if (isSubarrayMountainForm(arr left right L R))  document.write('Subarray is in ' + 'mountain form' + '
'
); else document.write('Subarray is not ' + 'in mountain form' + '
'
); L = 1; R = 3; if (isSubarrayMountainForm(arr left right L R)) document.write('Subarray is in ' + 'mountain form'); else document.write('Subarray is not ' + 'in mountain form'); </script>
    Išvestis:
Subarray is in mountain form Subarray is not in mountain form
    Sudėtingumo analizė: 
      Laiko sudėtingumas:O(n). 
      Reikia tik dviejų perėjimų, todėl laiko sudėtingumas yra O (n).Erdvės sudėtingumas:O(n). 
      Reikia dviejų papildomų n ilgio erdvių, kad erdvės sudėtingumas būtų O(n).


 

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