Minimum product in a grid of adjacent elements

Given an N x M grid. The task is to find the minimum product of four adjacent numbers in the same direction (up, down, left, right, or diagonally) in the matrix. 

Examples:

Input : mat[][] = {1, 2, 3, 4,
                   5, 6, 7, 8,
                   9, 10, 11, 12}  
Output : 700 
2*5*7*10 gives output as 700 which is the smallest 
product possible 

Input : mat[][] = {7, 6, 7, 9
        1, 2, 3, 4
        1, 2, 3, 6,
        5, 6, 7, 1}   
Output: 36   

Approach: Traverse in the matrix apart from the first row, last row, first column, and last column. Compute the product of the four adjacent numbers, which are mat[i-1][j], mat[i+1][j], mat[i][j+1] and mat[i][j-1]. In each computation, if the product thus formed is less than the previous minimum found, then replace the minimum variable with the computed product. 

Below is the implementation of the above approach: 

C++

// C++ program to find the minimum product
// of adjacent elements
#include <bits/stdc++.h>
using namespace std;
const int N = 3;
const int M = 4;

// Function to return the minimum
// product of adjacent elements
int minimumProduct(int mat[N][M])
{

    // initial minimum
    int minimum = INT_MAX;

    // Traverse in the matrix
    // except the first, last row
    // first and last column
    for (int i = 1; i < N - 1; i++) {
        for (int j = 1; j < M - 1; j++) {
            // product the adjacent elements
            int p = mat[i - 1][j] * mat[i + 1][j]
                    * mat[i][j + 1] * mat[i][j - 1];

            // if the product is less than
            // the previously computed minimum
            if (p < minimum)
                minimum = p;
        }
    }

    return minimum;
}

// Driver Code
int main()
{
    int mat[][4] = { { 1, 2, 3, 4 },
                     { 4, 5, 6, 7 },
                     { 7, 8, 9, 12 } };

    cout << minimumProduct(mat);
    return 0;
}

Java

// Java program to find
// the minimum product
// of adjacent elements
import java.io.*;

class GFG
{
static int N = 3;
static int M = 4;

// Function to return the
// minimum product of
// adjacent elements
static int minimumProduct(int mat[][])
{

    // initial minimum
    int minimum = Integer.MAX_VALUE;

    // Traverse in the matrix
    // except the first, last row
    // first and last column
    for (int i = 1; i < N - 1; i++)
    {
        for (int j = 1; j < M - 1; j++)
        {
            // product the
            // adjacent elements
            int p = mat[i - 1][j] *
                    mat[i + 1][j] *
                    mat[i][j + 1] *
                    mat[i][j - 1];

            // if the product is less
            // than the previously
            // computed minimum
            if (p < minimum)
                minimum = p;
        }
    }

    return minimum;
}

// Driver Code
public static void main (String[] args)
{
    int mat[][] = {{1, 2, 3, 4},
                   {4, 5, 6, 7},
                   {7, 8, 9, 12}};

    System.out.println(minimumProduct(mat));
}
}

// This code is contributed
// by anuj_67.

Python3

# Python 3 program to find the minimum
# product of adjacent elements
import sys

N = 3
M = 4

# Function to return the minimum
# product of adjacent elements
def minimumProduct(mat):

    # initial minimum
    minimum = sys.maxsize

    # Traverse in the matrix except
    # the first, last row first
    # and last column
    for i in range(1, N - 1, 1):
        for j in range(1, M - 1, 1):

            # product the adjacent elements
            p = (mat[i - 1][j] * mat[i + 1][j] *
                 mat[i][j + 1] * mat[i][j - 1])

            # if the product is less than
            # the previously computed minimum
            if (p < minimum):
                minimum = p

    return minimum

# Driver Code
if __name__ == '__main__':
    mat = [[1, 2, 3, 4],
           [4, 5, 6, 7],
           [7, 8, 9, 12]]

    print(minimumProduct(mat))

# This code is contributed by
# Shashank_Sharma

C#

// C# program to find
// the minimum product
// of adjacent elements
using System;

class GFG
{
static int N = 3;
static int M = 4;

// Function to return the
// minimum product of
// adjacent elements
static int minimumProduct(int [,]mat)
{

    // initial minimum
    int minimum = int.MaxValue;

    // Traverse in the matrix
    // except the first, last row
    // first and last column
    for (int i = 1;
             i < N - 1; i++)
    {
        for (int j = 1;
                 j < M - 1; j++)
        {
            // product the
            // adjacent elements
            int p = mat[i - 1, j] *
                    mat[i + 1, j] *
                    mat[i, j + 1] *
                    mat[i, j - 1];

            // if the product is less
            // than the previously
            // computed minimum
            if (p < minimum)
                minimum = p;
        }
    }

    return minimum;
}

// Driver Code
public static void Main ()
{
    int [,]mat = {{1, 2, 3, 4},
                  {4, 5, 6, 7},
                  {7, 8, 9, 12}};

    Console.WriteLine(minimumProduct(mat));
}
}

// This code is contributed
// by anuj_67.

PHP

<?php
// PHP program to find the minimum
// product of adjacent elements
$N = 3;
$M = 4;

// Function to return the minimum
// product of adjacent elements
function minimumProduct($mat)
{
    global $N;
    global $M;

    // initial minimum
    $minimum = PHP_INT_MAX;

    // Traverse in the matrix
    // except the first, last row
    // first and last column
    for ($i = 1; $i < $N - 1; $i++)
    {
        for ($j = 1; $j < $M - 1; $j++)
        {
            // product the adjacent elements
            $p = $mat[$i - 1][$j] * $mat[$i + 1][$j] *
                 $mat[$i][$j + 1] * $mat[$i][$j - 1];

            // if the product is less than the
            // previously computed minimum
            if ($p < $minimum)
                $minimum = $p;
        }
    }

    return $minimum;
}

// Driver Code
$mat = array(array(1, 2, 3, 4),
             array(4, 5, 6, 7),
             array(7, 8, 9, 12));

echo minimumProduct($mat);

// This code is contributed by Sach_Code
?>

Javascript

<script>
    // Javascript program to find
    // the minimum product
    // of adjacent elements

    let N = 3;
    let M = 4;

    // Function to return the
    // minimum product of
    // adjacent elements
    function minimumProduct(mat)
    {

        // initial minimum
        let minimum = Number.MAX_VALUE;

        // Traverse in the matrix
        // except the first, last row
        // first and last column
        for (let i = 1; i < N - 1; i++)
        {
            for (let j = 1; j < M - 1; j++)
            {
                // product the
                // adjacent elements
                let p = mat[i - 1][j] *
                        mat[i + 1][j] *
                        mat[i][j + 1] *
                        mat[i][j - 1];

                // if the product is less
                // than the previously
                // computed minimum
                if (p < minimum)
                    minimum = p;
            }
        }

        return minimum;
    }

    let mat = [[1, 2, 3, 4],
               [4, 5, 6, 7],
               [7, 8, 9, 12]];

    document.write(minimumProduct(mat));

</script>

Output

384

Time Complexity: O(N*M), where N and M are the number of rows and columns in the given matrix
Auxiliary Space: O(1)