Which approach guarantees an optimal time complexity solution?
easy🔍 Pattern Recognition Q11 of Q15
Intervals - Interval List Intersections
Given two lists of closed intervals, each sorted and non-overlapping within themselves, you need to find all intervals where the two lists overlap. Which approach guarantees an optimal time complexity solution?
AUse a brute force nested loop to compare every interval in the first list with every interval in the second list.
BUse two pointers to traverse both lists simultaneously, advancing the pointer with the smaller interval endpoint to find intersections efficiently.
CSort all intervals from both lists together and then merge overlapping intervals to find intersections.
DUse dynamic programming to store and compute overlapping intervals between the two lists.
Step-by-Step Solution
Step 1: Understand problem constraints
Both lists are sorted and non-overlapping internally, so a linear scan is possible.
Step 2: Identify the optimal approach
Two pointers allow simultaneous traversal, comparing intervals in O(m + n) time, advancing pointers based on interval endpoints.
Final Answer:
Option B -> Option B
Quick Check:
Two pointers avoid unnecessary comparisons and achieve linear time [OK]
Quick Trick:Two pointers exploit sorted order for linear time [OK]
Common Mistakes:
MISTAKES
Assuming brute force is acceptable
Thinking sorting combined lists is needed
Misapplying DP to interval intersection
Trap Explanation:
PITFALL
Brute force looks straightforward but is O(m*n), sorting combined lists adds unnecessary overhead, DP is unrelated here.
Interviewer Note:
CONTEXT
Tests if candidate recognizes the two pointers pattern for interval problems.
Master "Interval List Intersections" in Intervals
3 interactive learning modes - each teaches the same concept differently
