Question

Given an array and a sum s find all pairs of numbers which whose sum = s ?

Answer 1

Answer:

Let Array be {1, 4, 45, 6, 10, -8} and sum to find be 16

Sort the array

A = {-8, 1, 4, 6, 10, 45}

Initialize l = 0, r = 5

A[l] + A[r] ( -8 + 45) > 16 => decrement r. Now r = 10

A[l] + A[r] ( -8 + 10) increment l. Now l = 1

A[l] + A[r] ( 1 + 10) increment l. Now l = 2

A[l] + A[r] ( 4 + 10) increment l. Now l = 3

A[l] + A[r] ( 6 + 10) == 16 => Found candidates (return 1)

Note: If there are more than one pair having the given sum then this algorithm reports only one. Can be easily extended for this though.

Hope it helps you.....