Replace every element with the smallest element on its left side

Last Updated : 17 Sep, 2022

Given an array of integers, the task is to replace every element with the smallest element on its left side.

Note: Replace the first element with -1 as it has no element in its left.

Examples:

Input: arr[] = {4, 5, 2, 1, 7, 6} Output: -1 4 4 2 1 1 Since, 4 has no element in its left, so replace it by -1. For 5, 4 is the smallest element in its left. For 2, 4 is the smallest element in its left. For 1, 2 is the smallest element in its left. For 7, 1 is the smallest element in its left. For 6, 1 is the smallest element in its left.  Input: arr[] = {3, 2, 5, 7, 1} Output: -1 3 2 2 2

Approach:

Maintain a variable min_ele which will store the smallest element.
Initially, min_ele will be equal to the element at the 0th index.
First replace arr[0] with -1 then traverse the array
And then replace the element with the min_ele value and update the min_ele if the element is smaller than min_ele.
Print the modified array.

Below is the implementation of the above approach:

C++

// C++ program to Replace every // element with the smaller element // on its left side #include <bits/stdc++.h> using namespace std;  // Function to replace the elements void ReplaceElements(int arr[], int n) {     // MIN value initialised     // to element at 0th index     int min_ele = arr[0];     arr[0] = -1;      for (int i = 1; i < n; ++i) {          // If min_ele is smaller than arr[i]         // then just replace arr[i] with min_ele         if (min_ele < arr[i])             arr[i] = min_ele;           // Else if update the min_ele also         else if (min_ele >= arr[i]) {             int temp = arr[i];             arr[i] = min_ele;             min_ele = temp;         }     } }  // Driver code int main() {     int arr[] = { 4, 5, 2, 1, 7, 6 };     int n = sizeof(arr) / sizeof(arr[0]);      // Replace the elements     // with the smaller element     // on its left side     ReplaceElements(arr, n);      // Print the modified array     for (int i = 0; i < n; ++i)         cout << arr[i] << " ";      return 0; }

Java

// Java program to Replace every  // element with the smaller element  // on its left side   class GFG {  // Function to replace the elements      static void ReplaceElements(int arr[], int n) {         // MIN value initialised          // to element at 0th index          int min_ele = arr[0];         arr[0] = -1;          for (int i = 1; i < n; ++i) {              // If min_ele is smaller than arr[i]              // then just replace arr[i] with min_ele              if (min_ele < arr[i]) {                 arr[i] = min_ele;             } // Else if update the min_ele also              else if (min_ele >= arr[i]) {                 int temp = arr[i];                 arr[i] = min_ele;                 min_ele = temp;             }         }     }  // Driver code      public static void main(String[] args) {         int arr[] = {4, 5, 2, 1, 7, 6};         int n = arr.length;          // Replace the elements          // with the smaller element          // on its left side          ReplaceElements(arr, n);          // Print the modified array          for (int i = 0; i < n; ++i) {             System.out.print(arr[i] + " ");         }     } }  // This code is contributed by Rajput-JI

Python3

# Python3 program to Replace every # element with the smaller element # on its left side  # Function to replace the elements def ReplaceElements(arr, n):      # MIN value initialised     # to element at 0th index     min_ele = arr[0]     arr[0] = -1      for i in range(1, n):          # If min_ele is smaller than arr[i]         # then just replace arr[i] with min_ele         if (min_ele < arr[i]):             arr[i] = min_ele          # Else if update the min_ele also         elif (min_ele >= arr[i]) :             temp = arr[i]             arr[i] = min_ele             min_ele = temp  # Driver code if __name__ == "__main__":      arr = [ 4, 5, 2, 1, 7, 6 ]     n = len (arr)      # Replace the elements     # with the smaller element     # on its left side     ReplaceElements(arr, n)      # Print the modified array     for i in range( n):         print (arr[i], end = " ")  # This code is contributed # by ChitraNayal

// C# program to Replace every  // element with the smaller element  // on its left side  using System; public class GFG {   // Function to replace the elements      static void ReplaceElements(int []arr, int n) {         // MIN value initialised          // to element at 0th index          int min_ele = arr[0];         arr[0] = -1;          for (int i = 1; i < n; ++i) {              // If min_ele is smaller than arr[i]              // then just replace arr[i] with min_ele              if (min_ele < arr[i]) {                 arr[i] = min_ele;             } // Else if update the min_ele also              else if (min_ele >= arr[i]) {                 int temp = arr[i];                 arr[i] = min_ele;                 min_ele = temp;             }         }     }  // Driver code      public static void Main() {         int []arr = {4, 5, 2, 1, 7, 6};         int n = arr.Length;          // Replace the elements          // with the smaller element          // on its left side          ReplaceElements(arr, n);          // Print the modified array          for (int i = 0; i < n; ++i) {             Console.Write(arr[i] + " ");         }     } }  // This code is contributed by Rajput-JI

PHP

<?php // PHP program to Replace every // element with the smaller element // on its left side  // Function to replace the elements function ReplaceElements($arr, $n) {     // MIN value initialised     // to element at 0th index     $min_ele = $arr[0];     $arr[0] = -1;      for ($i = 1; $i < $n; ++$i)      {          // If min_ele is smaller than arr[i]         // then just replace arr[i] with min_ele         if ($min_ele < $arr[$i])             $arr[$i] = $min_ele;          // Else if update the min_ele also         else if ($min_ele >= $arr[$i])         {             $temp = $arr[$i];             $arr[$i] = $min_ele;             $min_ele = $temp;         }     }     return $arr; }  // Driver code $arr = array(4, 5, 2, 1, 7, 6); $n = sizeof($arr);  // Replace the elements // with the smaller element // on its left side $arr1 = ReplaceElements($arr, $n);  // Print the modified array for ($i = 0; $i < $n; ++$i)     echo $arr1[$i] . " ";  // This code is contributed  // by Akanksha Rai ?>

JavaScript

<script>       // JavaScript program to Replace every       // element with the smaller element       // on its left side        // Function to replace the elements       function ReplaceElements(arr, n)        {                // MIN value initialised         // to element at 0th index         var min_ele = arr[0];         arr[0] = -1;          for (var i = 1; i < n; ++i)          {                    // If min_ele is smaller than arr[i]           // then just replace arr[i] with min_ele           if (min_ele < arr[i]) arr[i] = min_ele;           // Else if update the min_ele also           else if (min_ele >= arr[i])            {             var temp = arr[i];             arr[i] = min_ele;             min_ele = temp;           }         }       }        // Driver code       var arr = [4, 5, 2, 1, 7, 6];       var n = arr.length;        // Replace the elements       // with the smaller element       // on its left side       ReplaceElements(arr, n);        // Print the modified array       for (var i = 0; i < n; ++i) document.write(arr[i] + " ");              // This code is contributed by rdtank.     </script>