Question

How to find the previous smaller element from the beginning of array for each array element in C++

Answer 1

#include <iostream>

void findPreviousSmaller(int arr[], int size) {
    for (int i = 0; i < size; i++) {
        int not_found = 1; // if not found write -1
   
        int previous_smaller = arr[i];
        for (int j = i - 1; j >= 0; j--) {
            if (arr[j] < previous_smaller) {
                previous_smaller = arr[j];
                not_found = 0;
            }
        }
   
        std::cout << ((not_found) ? -1 : previous_smaller) << " ";
    }
}
   
int main(void)
{
    int arr[] = { 2, 6, 3, 7, 8, 1, 9, 0, 13, 19, 18 };
      
    // 2:-1 // 6:2 // 3:2 // 7:2 // 8:2 // 1:-1 // 9:1 // 0:-1 // 13:0 // 19:0 // 18:0
   
    findPreviousSmaller(arr, sizeof(arr) / sizeof(arr[0]));
   
    return 0;
}
  
 
  
  
/*
run:
 
-1 2 2 2 2 -1 1 -1 0 0 0 
 
*/

 

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