SDE - Intern

You are given an array 'ARR' of integers. Your task is to modify the array so that all the array elements having zero values get pushed to the left and all the array elements having non-zero value come after them while maintaining their relative order.

For example :

Consider the array { 1, 1, 0, 2, 0 }. 
For the given array the modified array should be {0,0,1,1,2} . 
Arrays { 0, 0, 1, 2, 1 } and  { 0, 0, 2, 1, 1 } are not the correctly reorganized array even if they have all the zero values pushed to the left as in both the arrays the relative order of non-zero elements is not maintained.

Follow Up :

Can you solve the problem in linear time, and constant space?

Difference delete and truncate
what DML languages
Sql vs no sql

You are given an array/list ‘ARR’ consisting of ‘N’ distinct integers arranged in ascending order. You are also given an integer ‘TARGET’. Your task is to count all the distinct pairs in ‘ARR’ such that their sum is equal to ‘TARGET’.

Note:

1. Pair (x,y) and Pair(y,x) are considered as the same pair. 

2. If there exists no such pair with sum equals to 'TARGET', then return -1.

Example:

Let ‘ARR’ = [1 2 3] and ‘TARGET’ = 4. Then, there exists only one pair in ‘ARR’ with a sum of 4 which is (1, 3). (1, 3) and (3, 1) are counted as only one pair.