Number of pairs with sum less than or equal to given value

Problem solving with programming: Number of pairs with sum less than or equal to given value
Given an array of numbers, Count the number of pairs with sum less than or equal to K

1. First sort the array in ascending order.
2. Take two indices one(b) pointing to the start of the array, and the other(e) pointing to the last element of the array.
3. If A[b]+A[e] <= K
1. All the elements between [b+1,e] also satisfy the given property.
2. Increment b and decrement e and repeat step 3
4. Otherwise decrement e
5. Repeat step 3 until b and e meet each other.

A[0] A[1] A[2]... A[N]
b-->            <--e

Considering the above example 

{1, 3, 5, 6, 12} let b = 0, e = 3 and K = 10

1  3  5  6  12
b        e
 
If we add 6 or 5 or 3 to 1, the sum is less than 10. At this point, we can increment the pair count in one shot. 

public static int getPairsWithSumOrLess(int[] array, int sum)


{


Arrays.sort(array);


int pairCount = 0;


for( int i = 0, j = array.length-1; i < j; )


{


if( array[i]+array[j] <= sum )


{


pairCount += j-i;


i++;


j--;


}


else


{


j--;


}


}


return pairCount;


}

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