Question

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

Answer 1

function findPreviousSmaller($arr) {
    $size = count($arr);
    for ($i = 0; $i < $size; $i++) {
        $not_found = 1; // if not found write -1
   
        $previous_smaller = $arr[$i];
        for ($j = $i - 1; $j >= 0; $j--) {
            if ($arr[$j] < $previous_smaller) {
                $previous_smaller = $arr[$j];
                $not_found = 0;
            }
        }
   
        echo (($not_found) ? -1 : $previous_smaller) . " ";
    }
}

$arr = array( 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);

 


/*
run:
 
-1 2 2 2 2 -1 1 -1 0 0 0 
 
*/

 

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