Exclusive Time of Functions

Given n functions and a list of logs (each log is "function_id:start/end:timestamp"), compute the exclusive execution time of each function.

Example 1

Input: n=2, logs=["0:start:0","1:start:2","1:end:5","0:end:6"] → Output: [3,4]

Example 2

Input: n=1, logs=["0:start:0","0:start:2","0:end:5","0:end:6"] → Output: [8]

Solution Approach

Use a stack to track the currently running function. On each log, if start: push function id and record time. If end: pop and add duration. Subtract paused time for nested functions.

Parse each log into (id, type, time).
Maintain a stack of function IDs and a prevTime variable.
On start: if stack non-empty, add (time - prevTime) to top function. Push id, prevTime = time.
On end: add (time - prevTime + 1) to current function. Pop stack, prevTime = time + 1.

Java

import java.util.*;

class Solution {
    public int[] exclusiveTime(int n, List<String> logs) {
        int[] result = new int[n];
        Deque<Integer> stack = new ArrayDeque<>();
        int prevTime = 0;
        for (String log : logs) {
            String[] parts = log.split(":");
            int id = Integer.parseInt(parts[0]);
            int time = Integer.parseInt(parts[2]);
            boolean isStart = parts[1].equals("start");
            if (isStart) {
                if (!stack.isEmpty()) result[stack.peek()] += time - prevTime;
                stack.push(id);
                prevTime = time;
            } else {
                result[stack.pop()] += time - prevTime + 1;
                prevTime = time + 1;
            }
        }
        return result;
    }
}

Time Complexity: O(N) where N = number of log entries
Space Complexity: O(N) stack