Exclusive Time of Functions
mediumTime: O(n)Space: O(n)
Signals to notice
track execution time of nested function callsexclusive time per functionstack for call hierarchy
Brute force first
Not applicable — the stack approach IS the natural solution for nested calls.
The key insight
Stack of function IDs. On start: push function, record timestamp. On end: pop, compute duration, subtract from parent's time. O(n).
What must stay true
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.
Easy way to go wrong
Not subtracting child time from parent — exclusive time means time spent directly in the function, not in its children.