LESSON 86 OF 349 · CONDITIONAL STATEMENTS - CHALLENGES

Interval Intersection in Swift

Practice

Given two closed intervals [A1, B1] and [A2, B2], check and return if the two intervals intersect each other.

A closed interval [a, b] (with a <= b) denotes the set of real numbers x with a <= x <= b.

Two closed intervals are said to intersect if they have common numbers, i.e. that appear in both intervals.

Example 1:

Input: A1 = 1, B1 = 6, A2 = 3, B2 = 8
Output: true

Example 2:

Input: A1 = 1, B1 = 4, A2 = 4, B2 = 6
Output: true

Example 3:

Input: A1 = 1, B1 = 8, A2 = 4, B2 = 6
Output: true

Example 4:

Input: A1 = 4, B1 = 6, A2 = 1, B2 = 3
Output: false

Note:

Your algorithm should run in O(1) time and use O(1) extra space.

Hints:

Instead of thinking about when the intervals intersect each other, it's easier to think about when they do not intersect each other.

The intervals do not intersect each other when one of them is "to the left" of the other one i.e. B1 < A2 or B2 < A1.

We can write an if statement checking if B1 < A2 or B2 < A1. If so, we return false. Otherwise, we return true.

You can implement this using no else statements. You can even implement it in one line using only one return.

STEP 1 OF 1

Guided

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