Php Program for Count pairs with given sum
Last Updated :
30 Dec, 2021
Given an array of integers, and a number ‘sum’, find the number of pairs of integers in the array whose sum is equal to ‘sum’.
Examples:Â Â
Input : arr[] = {1, 5, 7, -1},
sum = 6
Output : 2
Pairs with sum 6 are (1, 5) and (7, -1)
Input : arr[] = {1, 5, 7, -1, 5},
sum = 6
Output : 3
Pairs with sum 6 are (1, 5), (7, -1) &
(1, 5)
Input : arr[] = {1, 1, 1, 1},
sum = 2
Output : 6
There are 3! pairs with sum 2.
Input : arr[] = {10, 12, 10, 15, -1, 7, 6,
5, 4, 2, 1, 1, 1},
sum = 11
Output : 9
Expected time complexity O(n)
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Naive Solution – A simple solution is to traverse each element and check if there’s another number in the array which can be added to it to give sum.Â
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PHP
<?php
function getPairsCount( $arr , $n , $sum )
{
$count = 0;
for ( $i = 0; $i < $n ; $i ++)
for ( $j = $i + 1; $j < $n ; $j ++)
if ( $arr [ $i ] + $arr [ $j ] == $sum )
$count ++;
return $count ;
}
$arr = array (1, 5, 7, -1, 5) ;
$n = sizeof( $arr );
$sum = 6;
echo "Count of pairs is "
, getPairsCount( $arr , $n , $sum );
?>
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Output
Count of pairs is 3
Time Complexity: O(n2)Â
Auxiliary Space: O(1)
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