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Queries to find the maximum and minimum array elements excluding elements from a given range
  • Last Updated : 15 Feb, 2021

Given an array arr[] consisting of N integers and an array Q[][] consisting of queries of the form [L, R]., the task for each query is to find the maximum and minimum array elements in the array excluding the elements from the given range.

Examples:

Input: arr[] = {2, 3, 1, 8, 3, 5, 7, 4}, Q[][] = {{4, 6}, {0, 4}, {3, 7}, {2, 5}}
Output: 
8 1
7 4
3 1
7 2
Explanation:
Query 1: max(arr[0, 1, …, 3], arr[7]) = 8 and min(arr[0, 1, …, 3], arr[7]) = 1
Query 2: max(arr[5, 6, …, 7]) = 7 and min(arr[5, 6, …, 7]) = 4
Query 3: max(arr[0, 1, …, 2]) =3 and min(arr[0, 1, …, 2]) = 1
Query 4: max(arr[0, 1], arr[6, …, 7]) =7 and min(arr[0, 1], arr[6, …, 7]) = 2

Input: arr[] = {3, 2, 1, 4, 5}, Q[][] = {{1, 2}, {2, 4}}
Output:
5 3
3 2

Naive Approach: The simplest approach to solve the problem is to traverse the array for each query, and find the maximum and minimum elements present outside the range of indices [L, R].
Time Complexity: O(N2)
Auxiliary Space: O(1)

Efficient Approach: Divide the problem into subtasks by dividing the array into sub-ranges and find the maximum and minimum value from arr[0] to arr[L – 1] and from arr[r + 1] to arr[N – 1] and store them in a prefix and a suffix array respectively. Now find the maximum and minimum values for the given ranges by comparing the prefix and the suffix array.
Follow the below steps:



  • Traverse the array and maintain maximum and minimum elements encountered for every index in a 2D prefix array by comparing the value at the current index with the maximum and minimum values of the previous index.
  • Now, iterate over the array in reverse and maintain maximum and minimum values for indices in 2D suffix array by comparing the value at the current index with the maximum and minimum values of the next index.
  • Now, for each query, perform the following steps: 
    • If L = 0 and R = N – 1, then no element remains after excluding the range.
    • Otherwise, if L = 0, the maximum and minimum value will be present between arr[R + 1] to arr[N – 1].
    • Otherwise, if R = N – 1, the maximum and minimum value will be present between arr[0] to arr[L – 1].
    • Otherwise, find the maximum and minimum values in the range arr[0] to arr[L – 1] and arr[R + 1] to arr[N – 1].
    • Print the maximum and minimum value for this query.

Below is the implementation of the above approach:

C++




// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;
 
// Function to find the maximum and
// minimum array elements up to the i-th index
void prefixArr(int arr[], int prefix[][2], int N)
{
 
    // Traverse the array
    for (int i = 0; i < N; i++) {
        if (i == 0) {
            prefix[i][0] = arr[i];
            prefix[i][1] = arr[i];
        }
 
        else {
 
            // Compare current value with maximum
            // and minimum values up to previous index
            prefix[i][0] = max(prefix[i - 1][0], arr[i]);
            prefix[i][1] = min(prefix[i - 1][1], arr[i]);
        }
    }
}
 
// Function to find the maximum and
// minimum array elements from i-th index
void suffixArr(int arr[], int suffix[][2], int N)
{
 
    // Traverse the array in reverse
    for (int i = N - 1; i >= 0; i--) {
 
        if (i == N - 1) {
            suffix[i][0] = arr[i];
            suffix[i][1] = arr[i];
        }
        else {
 
            // Compare current value with maximum
            // and minimum values in the next index
            suffix[i][0] = max(suffix[i + 1][0], arr[i]);
            suffix[i][1] = min(suffix[i + 1][1], arr[i]);
        }
    }
}
 
// Function to find the maximum and
// minimum array elements for each query
void maxAndmin(int prefix[][2],
               int suffix[][2],
               int N, int L, int R)
{
 
    int maximum, minimum;
 
    // If no index remains after
    // excluding the elements
    // in a given range
    if (L == 0 && R == N - 1) {
        cout << "No maximum and minimum value" << endl;
        return;
    }
 
    // Find maximum and minimum from
    // from the range [R + 1, N - 1]
    else if (L == 0) {
        maximum = suffix[R + 1][0];
        minimum = suffix[R + 1][1];
    }
 
    // Find maximum and minimum from
    // from the range [0, N - 1]
    else if (R == N - 1) {
        maximum = prefix[L - 1][0];
        minimum = prefix[R - 1][1];
    }
 
    // Find maximum and minimum values from the
    // ranges [0, L - 1] and [R + 1, N - 1]
    else {
        maximum = max(prefix[L - 1][0],
                      suffix[R + 1][0]);
        minimum = min(prefix[L - 1][1],
                      suffix[R + 1][1]);
    }
 
    // Print the maximum and minimum value
    cout << maximum << " " << minimum << endl;
}
 
// Function to perform queries to find the
// minimum and maximum array elements excluding
// elements from a given range
void MinMaxQueries(int a[], int Q[][])
{
 
    // Size of the array
    int N = sizeof(arr) / sizeof(arr[0]);
 
    // Size of query array
    int q = sizeof(queries) / sizeof(queries[0]);
 
    // prefix[i][0]: Stores the maximum
    // prefix[i][1]: Stores the minimum value
    int prefix[N][2];
 
    // suffix[i][0]: Stores the maximum
    // suffix[i][1]: Stores the minimum value
    int suffix[N][2];
 
    // Function calls to store
    // maximum and minimum values
    // for respective ranges
    prefixArr(arr, prefix, N);
    suffixArr(arr, suffix, N);
 
    for (int i = 0; i < q; i++) {
 
        int L = queries[i][0];
        int R = queries[i][1];
 
        maxAndmin(prefix, suffix, N, L, R);
    }
}
 
// Driver Code
int main()
{
 
    // Given array
    int arr[] = { 2, 3, 1, 8, 3, 5, 7, 4 };
 
    int queries[][2]
        = { { 4, 6 }, { 0, 4 }, { 3, 7 }, { 2, 5 } };
 
    MinMaxQueries(arr, Q);
 
    return 0;
}

Java




// Java program for the above approach
public class GFG
{
 
  // Function to find the maximum and
  // minimum array elements up to the i-th index
  static void prefixArr(int arr[], int prefix[][], int N)
  {
 
    // Traverse the array
    for (int i = 0; i < N; i++)
    {
      if (i == 0)
      {
        prefix[i][0] = arr[i];
        prefix[i][1] = arr[i];
      }
      else
      {
 
        // Compare current value with maximum
        // and minimum values up to previous index
        prefix[i][0] = Math.max(prefix[i - 1][0], arr[i]);
        prefix[i][1] = Math.min(prefix[i - 1][1], arr[i]);
      }
    }
  }
 
  // Function to find the maximum and
  // minimum array elements from i-th index
  static void suffixArr(int arr[], int suffix[][], int N)
  {
 
    // Traverse the array in reverse
    for (int i = N - 1; i >= 0; i--)
    {
      if (i == N - 1)
      {
        suffix[i][0] = arr[i];
        suffix[i][1] = arr[i];
      }
      else
      {
 
        // Compare current value with maximum
        // and minimum values in the next index
        suffix[i][0] = Math.max(suffix[i + 1][0], arr[i]);
        suffix[i][1] = Math.min(suffix[i + 1][1], arr[i]);
      }
    }
  }
 
  // Function to find the maximum and
  // minimum array elements for each query
  static void maxAndmin(int prefix[][],
                        int suffix[][],
                        int N, int L, int R)
  {
    int maximum, minimum;
 
    // If no index remains after
    // excluding the elements
    // in a given range
    if (L == 0 && R == N - 1)
    {
      System.out.println("No maximum and minimum value");
      return;
    }
 
    // Find maximum and minimum from
    // from the range [R + 1, N - 1]
    else if (L == 0)
    {
      maximum = suffix[R + 1][0];
      minimum = suffix[R + 1][1];
    }
 
    // Find maximum and minimum from
    // from the range [0, N - 1]
    else if (R == N - 1)
    {
      maximum = prefix[L - 1][0];
      minimum = prefix[R - 1][1];
    }
 
    // Find maximum and minimum values from the
    // ranges [0, L - 1] and [R + 1, N - 1]
    else
    {
      maximum = Math.max(prefix[L - 1][0],
                         suffix[R + 1][0]);
      minimum = Math.min(prefix[L - 1][1],
                         suffix[R + 1][1]);
    }
 
    // Print the maximum and minimum value
    System.out.println(maximum + " " + minimum);
  }
 
  // Function to perform queries to find the
  // minimum and maximum array elements excluding
  // elements from a given range
  static void MinMaxQueries(int a[], int Q[][])
  {
 
    // Size of the array
    int N = a.length;
 
    // Size of query array
    int q = Q.length;
 
    // prefix[i][0]: Stores the maximum
    // prefix[i][1]: Stores the minimum value
    int prefix[][] = new int[N][2];
 
    // suffix[i][0]: Stores the maximum
    // suffix[i][1]: Stores the minimum value
    int suffix[][] = new int[N][2];
 
    // Function calls to store
    // maximum and minimum values
    // for respective ranges
    prefixArr(a, prefix, N);
    suffixArr(a, suffix, N);
 
    for (int i = 0; i < q; i++)
    {
      int L = Q[i][0];
      int R = Q[i][1];
      maxAndmin(prefix, suffix, N, L, R);
    }
  }
 
  // Driver Code
  public static void main (String[] args)
  {
 
    // Given array
    int arr[] = { 2, 3, 1, 8, 3, 5, 7, 4 };
 
    int queries[][]
      = { { 4, 6 }, { 0, 4 }, { 3, 7 }, { 2, 5 } };
 
    MinMaxQueries(arr, queries);
  }
}
 
// This code is contributed by AnkThon

Python3




# Python3 program for the above approach
 
# Function to find the maximum and
# minimum array elements up to the i-th index
def prefixArr(arr, prefix, N):
 
    # Traverse the array
    for i in range(N):
        if (i == 0):
            prefix[i][0] = arr[i]
            prefix[i][1] = arr[i]
 
        else:
 
            # Compare current value with maximum
            # and minimum values up to previous index
            prefix[i][0] = max(prefix[i - 1][0], arr[i])
            prefix[i][1] = min(prefix[i - 1][1], arr[i])
    return prefix
 
 
# Function to find the maximum and
# minimum array elements from i-th index
def suffixArr(arr, suffix, N):
 
    # Traverse the array in reverse
    for i in range(N - 1, -1, -1):
 
        if (i == N - 1):
            suffix[i][0] = arr[i]
            suffix[i][1] = arr[i]
 
        else:
 
            # Compare current value with maximum
            # and minimum values in the next index
            suffix[i][0] = max(suffix[i + 1][0], arr[i])
            suffix[i][1] = min(suffix[i + 1][1], arr[i])
    return suffix
 
# Function to find the maximum and
# minimum array elements for each query
def maxAndmin(prefix, suffix, N, L, R):
    maximum, minimum = 0, 0
 
    # If no index remains after
    # excluding the elements
    # in a given range
    if (L == 0 and R == N - 1):
        print("No maximum and minimum value")
        return
 
    # Find maximum and minimum from
    # from the range [R + 1, N - 1]
    elif (L == 0):
        maximum = suffix[R + 1][0]
        minimum = suffix[R + 1][1]
 
    # Find maximum and minimum from
    # from the range [0, N - 1]
    elif (R == N - 1):
        maximum = prefix[L - 1][0]
        minimum = prefix[R - 1][1]
 
    # Find maximum and minimum values from the
    # ranges [0, L - 1] and [R + 1, N - 1]
    else:
        maximum = max(prefix[L - 1][0], suffix[R + 1][0])
        minimum = min(prefix[L - 1][1], suffix[R + 1][1])
 
    # Prthe maximum and minimum value
    print(maximum, minimum)
 
# Function to perform queries to find the
# minimum and maximum array elements excluding
# elements from a given range
def MinMaxQueries(a, queries):
 
    # Size of the array
    N = len(arr)
 
    # Size of query array
    q = len(queries)
 
    # prefix[i][0]: Stores the maximum
    # prefix[i][1]: Stores the minimum value
    prefix = [ [ 0 for i in range(2)] for i in range(N)]
 
    # suffix[i][0]: Stores the maximum
    # suffix[i][1]: Stores the minimum value
    suffix = [ [ 0 for i in range(2)] for i in range(N)]
 
    # Function calls to store
    # maximum and minimum values
    # for respective ranges
    prefix = prefixArr(arr, prefix, N)
    suffix = suffixArr(arr, suffix, N)
 
    for i in range(q):
        L = queries[i][0]
        R = queries[i][1]
 
        maxAndmin(prefix, suffix, N, L, R)
 
# Driver Code
if __name__ == '__main__':
 
    # Given array
    arr = [ 2, 3, 1, 8, 3, 5, 7, 4 ]
    queries = [ [ 4, 6 ], [ 0, 4 ], [ 3, 7 ], [ 2, 5 ] ]
    MinMaxQueries(arr, queries)
 
    # This code is contributed by mohit kumar 29.

C#




// C# program for the above approach
using System;
public class GFG
{
 
  // Function to find the maximum and
  // minimum array elements up to the i-th index
  static void prefixArr(int[] arr, int[,] prefix, int N)
  {
 
    // Traverse the array
    for (int i = 0; i < N; i++)
    {
      if (i == 0)
      {
        prefix[i, 0] = arr[i];
        prefix[i, 1] = arr[i];
      }
      else
      {
 
        // Compare current value with maximum
        // and minimum values up to previous index
        prefix[i, 0] = Math.Max(prefix[i - 1, 0], arr[i]);
        prefix[i, 1] = Math.Min(prefix[i - 1, 1], arr[i]);
      }
    }
  }
 
  // Function to find the maximum and
  // minimum array elements from i-th index
  static void suffixArr(int[] arr, int[,] suffix, int N)
  {
 
    // Traverse the array in reverse
    for (int i = N - 1; i >= 0; i--)
    {
      if (i == N - 1)
      {
        suffix[i, 0] = arr[i];
        suffix[i, 1] = arr[i];
      }
      else
      {
 
        // Compare current value with maximum
        // and minimum values in the next index
        suffix[i, 0] = Math.Max(suffix[i + 1, 0], arr[i]);
        suffix[i, 1] = Math.Min(suffix[i + 1, 1], arr[i]);
      }
    }
  }
 
  // Function to find the maximum and
  // minimum array elements for each query
  static void maxAndmin(int[,] prefix,
                        int[,] suffix,
                        int N, int L, int R)
  {
    int maximum, minimum;
 
    // If no index remains after
    // excluding the elements
    // in a given range
    if (L == 0 && R == N - 1)
    {
      Console.WriteLine("No maximum and minimum value");
      return;
    }
 
    // Find maximum and minimum from
    // from the range [R + 1, N - 1]
    else if (L == 0)
    {
      maximum = suffix[R + 1, 0];
      minimum = suffix[R + 1, 1];
    }
 
    // Find maximum and minimum from
    // from the range [0, N - 1]
    else if (R == N - 1)
    {
      maximum = prefix[L - 1, 0];
      minimum = prefix[R - 1, 1];
    }
 
    // Find maximum and minimum values from the
    // ranges [0, L - 1] and [R + 1, N - 1]
    else
    {
      maximum = Math.Max(prefix[L - 1, 0],
                         suffix[R + 1, 0]);
      minimum = Math.Min(prefix[L - 1, 1],
                         suffix[R + 1, 1]);
    }
 
    // Print the maximum and minimum value
    Console.WriteLine(maximum + " " + minimum);
  }
 
  // Function to perform queries to find the
  // minimum and maximum array elements excluding
  // elements from a given range
  static void MinMaxQueries(int[] a, int[,] Q)
  {
 
    // Size of the array
    int N = a.GetLength(0);
 
    // Size of query array
    int q = Q.GetLength(0);
 
    // prefix[i][0]: Stores the maximum
    // prefix[i][1]: Stores the minimum value
    int[,] prefix = new int[N, 2];
 
    // suffix[i][0]: Stores the maximum
    // suffix[i][1]: Stores the minimum value
    int[,] suffix = new int[N, 2];
 
    // Function calls to store
    // maximum and minimum values
    // for respective ranges
    prefixArr(a, prefix, N);
    suffixArr(a, suffix, N);
 
    for (int i = 0; i < q; i++)
    {
      int L = Q[i, 0];
      int R = Q[i, 1];
      maxAndmin(prefix, suffix, N, L, R);
    }
  }
 
  // Driver Code
  static public void Main ()
  {
     
    // Given array
    int[] arr = { 2, 3, 1, 8, 3, 5, 7, 4 };
    int[,] queries = { { 4, 6 }, { 0, 4 },
                      { 3, 7 }, { 2, 5 } };
    MinMaxQueries(arr, queries);
  }
}
 
// This code is contributed by sanjoy_62.

 
 

Output: 
8 1
7 4
3 1
7 2

 

Time Complexity: O(N)
Auxiliary Space: O(N)

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