Exclusive Time of Functions
mediumTime: O(n)Space: O(n)
Recognize the pattern
track execution time of nested function callsexclusive time per functionstack for call hierarchy
Brute force idea
Not applicable — the stack approach IS the natural solution for nested calls.
Better approach
Stack of function IDs. On start: push function, record timestamp. On end: pop, compute duration, subtract from parent's time. O(n).
Key invariant
The stack represents the active call chain. When a function ends, its duration is added to its total. The parent function's exclusive time excludes child durations.
Watch out for
Not subtracting child time from parent — exclusive time means time spent directly in the function, not in its children.