Problem: Count Pairs Whose Sum is Less than Target

Medium

30 min

Explore how to use the two pointers approach to count all distinct pairs in an array where the sum of elements is less than a target value. This lesson helps you apply an efficient linear-time strategy to solve problems involving pair sums and understand key problem-solving patterns for coding interviews.

Statement

You are given a 0-indexed integer array, nums, of length $n$ , and an integer target. Your task is to determine the number of distinct pairs of indexes $(i, j)$ such that:

$0 \leq i < j < n$ (i.e., $i$ comes before $j$ in the array)
The sum of the elements of the indexes $(i, j)$ , (i.e., $\text{nums}[i] + \text{nums}[j]$ ), is strictly less than the target.

Constraints:

$n =$ nums.length
$1 \leq n\leq 50$
$-50 \leq$ nums[i], target $\leq 50$

Problem: Count Pairs Whose Sum is Less than Target

Medium

30 min

Statement

You are given a 0-indexed integer array, nums, of length $n$ , and an integer target. Your task is to determine the number of distinct pairs of indexes $(i, j)$ such that:

$0 \leq i < j < n$ (i.e., $i$ comes before $j$ in the array)
The sum of the elements of the indexes $(i, j)$ , (i.e., $\text{nums}[i] + \text{nums}[j]$ ), is strictly less than the target.

Constraints:

$n =$ nums.length
$1 \leq n\leq 50$
$-50 \leq$ nums[i], target $\leq 50$

Problem: Count Pairs Whose Sum is Less than Target

Statement

Examples

Understand the problem

Figure it out!

Try it yourself

Problem: Count Pairs Whose Sum is Less than Target

Statement

Examples

Understand the problem

Figure it out!

Try it yourself