PHP Program for Largest Sum Contiguous Subarray

Write an efficient program to find the sum of contiguous subarray within a one-dimensional array of numbers which has the largest sum.

kadane-algorithm

Recommended: Please solve it on “PRACTICE ” first, before moving on to the solution.

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<?php
// PHP program to print largest
// contiguous array sum
  
function maxSubArraySum($a, $size)
{
    $max_so_far = PHP_INT_MIN; 
    $max_ending_here = 0;
  
    for ($i = 0; $i < $size; $i++)
    {
        $max_ending_here = $max_ending_here + $a[$i];
        if ($max_so_far < $max_ending_here)
            $max_so_far = $max_ending_here;
  
        if ($max_ending_here < 0)
            $max_ending_here = 0;
    }
    return $max_so_far;
}
  
// Driver code
$a = array(-2, -3, 4, -1,
           -2, 1, 5, -3);
$n = count($a);
$max_sum = maxSubArraySum($a, $n);
echo "Maximum contiguous sum is "
                          $max_sum;
  
// This code is contributed by anuj_67.
?>

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Output:



Maximum contiguous sum is 7

Above program can be optimized further, if we compare max_so_far with max_ending_here only if max_ending_here is greater than 0.

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<?php 
function maxSubArraySum(&$a, $size)
{
$max_so_far = 0;
$max_ending_here = 0;
for ($i = 0; $i < $size; $i++)
{
    $max_ending_here = $max_ending_here + $a[$i];
    if ($max_ending_here < 0)
        $max_ending_here = 0;
  
    /* Do not compare for all elements. 
       Compare only when max_ending_here > 0 */
    else if ($max_so_far < $max_ending_here)
        $max_so_far = $max_ending_here;
}
return $max_so_far;
  
// This code is contributed
// by ChitraNayal
?>

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Please refer complete article on Largest Sum Contiguous Subarray for more details!



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