Given a set, we need to find maximum and minimum possible product among all subsets of the set.
Examples:
Input : arr[] = {4, -2, 5};
Output: Maximum product = 20
Minimum product = -40
Maximum product is obtained by multiplying
4 5
Minimum product is obtained by multiplying
4, -2, 5
Input : arr[] = {-4, -2, 3, 7, 5, 0, 1};
Output: Maximum product = 840
Minimum product = -420
Maximum product is obtained by multiplying
-4, -2, 3, 7, 5
Minimum product is obtained by multiplying
-4, 3, 7, 5
As array can have negative value, zero and positive value, this problem can have lot of edge cases, if not attacked properly. Below given solution maintains maximum product and minimum product at current index and previous index and at any instant current product takes value from previous max or previous min multiplied with current element, depending on the sign of current element. For example, if we are finding maximum product then current maximum will be previous max times current value if current element is positive otherwise previous min times current value if current element is negative. Same procedure is applied for finding minimum product also.
Please see below simple code to understand.
C++
// C++ program to find maximum and minimum // product from an array #include <bits/stdc++.h> using namespace std; // method returns maximum and minimum obtainable // product of array arr pair<int, int> getMaxandMinProduct(int arr[], int n) { // Initialize all products with arr[0] int curMaxProduct = arr[0]; int curMinProduct = arr[0]; int prevMaxProduct = arr[0]; int prevMinProduct = arr[0]; int maxProduct = arr[0]; int minProduct = arr[0]; // Process all elements after arr[0] for (int i = 1; i < n; ++i) { /* Current maximum product is maximum of following 1) prevMax * curelement (when curelement is +ve) 2) prevMin * curelement (when curelement is -ve) 3) Element itself 4) Previous max product */ curMaxProduct = max(prevMaxProduct * arr[i], max(prevMinProduct * arr[i], arr[i])); curMaxProduct = max(curMaxProduct, prevMaxProduct); /* Current min product computation is Similar to that of current max product */ curMinProduct = min(prevMaxProduct * arr[i], min(prevMinProduct * arr[i], arr[i])); curMinProduct = min(curMinProduct, prevMinProduct); maxProduct = max(maxProduct, curMaxProduct); minProduct = min(minProduct, curMinProduct); // copy current values to previous values prevMaxProduct = curMaxProduct; prevMinProduct = curMinProduct; } return make_pair(minProduct, maxProduct); } // driver code to test above methods int main() { int arr[] = {-4, -2, 3, 7, 5, 0, 1}; int n = sizeof(arr) / sizeof(int); pair<int, int> product = getMaxandMinProduct(arr, n); printf("Minimum product is %d and " "Maximum product is %dn", product.first, product.second); return 0; } |
Java
// Java program to find maximum and minimum // product from an array class GFG { static class pair { int first, second; public pair(int first, int second) { this.first = first; this.second = second; } } // method returns maximum and minimum obtainable // product of array arr static pair getMaxandMinProduct(int arr[], int n) { // Initialize all products with arr[0] int curMaxProduct = arr[0]; int curMinProduct = arr[0]; int prevMaxProduct = arr[0]; int prevMinProduct = arr[0]; int maxProduct = arr[0]; int minProduct = arr[0]; // Process all elements after arr[0] for (int i = 1; i < n; ++i) { /* Current maximum product is maximum of following 1) prevMax * curelement (when curelement is +ve) 2) prevMin * curelement (when curelement is -ve) 3) Element itself 4) Previous max product */ curMaxProduct = Math.max(prevMaxProduct * arr[i], Math.max(prevMinProduct * arr[i], arr[i])); curMaxProduct = Math.max(curMaxProduct, prevMaxProduct); /* Current min product computation is Similar to that of current max product */ curMinProduct = Math.min(prevMaxProduct * arr[i], Math.min(prevMinProduct * arr[i], arr[i])); curMinProduct = Math.min(curMinProduct, prevMinProduct); maxProduct = Math.max(maxProduct, curMaxProduct); minProduct = Math.min(minProduct, curMinProduct); // copy current values to previous values prevMaxProduct = curMaxProduct; prevMinProduct = curMinProduct; } return new pair(minProduct, maxProduct); } // Driver Code public static void main(String[] args) { int arr[] = {-4, -2, 3, 7, 5, 0, 1}; int n = arr.length; pair product = getMaxandMinProduct(arr, n); System.out.printf("Minimum product is %d and " + "Maximum product is %d", product.first, product.second); } } // This code is contributed by Rajput-Ji |
Python3
# Python3 program to find maximum and # minimum product from an array # method returns maximum and minimum # obtainable product of array arr def getMaxandMinProduct(arr, n): # Initialize all products with arr[0] curMaxProduct = arr[0] curMinProduct = arr[0] prevMaxProduct = arr[0] prevMinProduct = arr[0] maxProduct = arr[0] minProduct = arr[0] # Process all elements after arr[0] for i in range(1, n): # Current maximum product is maximum of following # 1) prevMax * curelement (when curelement is +ve) # 2) prevMin * curelement (when curelement is -ve) # 3) Element itself # 4) Previous max product curMaxProduct = max(prevMaxProduct * arr[i], max(prevMinProduct * arr[i], arr[i])) curMaxProduct = max(curMaxProduct, prevMaxProduct) # Current min product computation is Similar to # that of current max product curMinProduct = min(prevMaxProduct * arr[i], min(prevMinProduct * arr[i], arr[i])) curMinProduct = min(curMinProduct, prevMinProduct) maxProduct = max(maxProduct, curMaxProduct) minProduct = min(minProduct, curMinProduct) # copy current values to previous values prevMaxProduct = curMaxProduct prevMinProduct = curMinProduct return (minProduct, maxProduct) # Driver Code if __name__ == "__main__": arr = [-4, -2, 3, 7, 5, 0, 1] n = len(arr) product = getMaxandMinProduct(arr, n) print("Minimum product is", product[0], "and", "Maximum product is", product[1]) # This code is contributed by # sanjeev2552 |
C#
// C# program to find maximum and minimum // product from an array using System; class GFG { public class pair { public int first, second; public pair(int first, int second) { this.first = first; this.second = second; } } // method returns maximum and minimum // obtainable product of array arr static pair getMaxandMinProduct(int []arr, int n) { // Initialize all products with arr[0] int curMaxProduct = arr[0]; int curMinProduct = arr[0]; int prevMaxProduct = arr[0]; int prevMinProduct = arr[0]; int maxProduct = arr[0]; int minProduct = arr[0]; // Process all elements after arr[0] for (int i = 1; i < n; ++i) { /* Current maximum product is maximum of following 1) prevMax * curelement (when curelement is +ve) 2) prevMin * curelement (when curelement is -ve) 3) Element itself 4) Previous max product */ curMaxProduct = Math.Max(prevMaxProduct * arr[i], Math.Max(prevMinProduct * arr[i], arr[i])); curMaxProduct = Math.Max(curMaxProduct, prevMaxProduct); /* Current min product computation is Similar to that of current max product */ curMinProduct = Math.Min(prevMaxProduct * arr[i], Math.Min(prevMinProduct * arr[i], arr[i])); curMinProduct = Math.Min(curMinProduct, prevMinProduct); maxProduct = Math.Max(maxProduct, curMaxProduct); minProduct = Math.Min(minProduct, curMinProduct); // copy current values to previous values prevMaxProduct = curMaxProduct; prevMinProduct = curMinProduct; } return new pair(minProduct, maxProduct); } // Driver Code public static void Main(String[] args) { int []arr = {-4, -2, 3, 7, 5, 0, 1}; int n = arr.Length; pair product = getMaxandMinProduct(arr, n); Console.Write("Minimum product is {0} and " + "Maximum product is {1}", product.first, product.second); } } // This code is contributed by Princi Singh |
Javascript
<script> // Javascript program to find maximum and minimum // product from an array // method returns maximum and minimum obtainable // product of array arr function getMaxandMinProduct(arr, n) { // Initialize all products with arr[0] let curMaxProduct = arr[0]; let curMinProduct = arr[0]; let prevMaxProduct = arr[0]; let prevMinProduct = arr[0]; let maxProduct = arr[0]; let minProduct = arr[0]; // Process all elements after arr[0] for(let i = 1; i < n; ++i) { /* Current maximum product is maximum of following 1) prevMax * curelement (when curelement is +ve) 2) prevMin * curelement (when curelement is -ve) 3) Element itself 4) Previous max product */ curMaxProduct = Math.max(prevMaxProduct * arr[i], Math.max(prevMinProduct * arr[i], arr[i])); curMaxProduct = Math.max(curMaxProduct, prevMaxProduct); /* Current min product computation is Similar to that of current max product */ curMinProduct = Math.min(prevMaxProduct * arr[i], Math.min(prevMinProduct * arr[i], arr[i])); curMinProduct = Math.min(curMinProduct, prevMinProduct); maxProduct = Math.max(maxProduct, curMaxProduct); minProduct = Math.min(minProduct, curMinProduct); // Copy current values to previous values prevMaxProduct = curMaxProduct; prevMinProduct = curMinProduct; } return [minProduct, maxProduct]; } // Driver code let arr = [ -4, -2, 3, 7, 5, 0, 1 ]; let n = arr.length; let product = getMaxandMinProduct(arr, n); document.write("Minimum product is " + product[0] + " and Maximum product is " + product[1]); // This code is contributed by _saurabh_jaiswal </script> |
Output
Minimum product is -420 and Maximum product is 840n
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