exclusive-time-of-functions.py

# Time:  O(n)
# Space: O(n)

# Given the running logs of n functions that are executed
# in a nonpreemptive single threaded CPU, find the exclusive time of these functions.
#
# Each function has a unique id, start from 0 to n-1.
# A function may be called recursively or by another function.
#
# A log is a string has this format : function_id:start_or_end:timestamp.
# For example, "0:start:0" means function 0 starts from the very beginning of time 0.
# "0:end:0" means function 0 ends to the very end of time 0.
#
# Exclusive time of a function is defined as the time spent within this function,
# the time spent by calling other functions should not be considered as
# this function's exclusive time.
# You should return the exclusive time of each function sorted by their function id.
#
# Example 1:
# Input:
# n = 2
# logs =
# ["0:start:0",
#  "1:start:2",
#  "1:end:5",
#  "0:end:6"]
# Output:[3, 4]
#
# Explanation:
# Function 0 starts at time 0, then it executes 2 units of time and reaches the end of time 1.
# Now function 0 calls function 1, function 1 starts at time 2, executes 4 units of time and end at time 5.
# Function 0 is running again at time 6, and also end at the time 6, thus executes 1 unit of time.
# So function 0 totally execute 2 + 1 = 3 units of time, and function 1 totally execute 4 units of time.
#
# Note:
# Input logs will be sorted by timestamp, NOT log id.
# Your output should be sorted by function id,
# which means the 0th element of your output corresponds to the exclusive time of function 0.
# Two functions won't start or end at the same time.
# Functions could be called recursively, and will always end.
# 1 <= n <= 100

class Solution(object):
    def exclusiveTime(self, n, logs):
        """
        :type n: int
        :type logs: List[str]
        :rtype: List[int]
        """
        result = [0] * n
        stk, prev = [], 0
        for log in logs:
            tokens = log.split(":")
            if tokens[1] == "start":
                if stk:
                    result[stk[-1]] += int(tokens[2]) - prev
                stk.append(int(tokens[0]))
                prev = int(tokens[2])
            else:
                result[stk.pop()] += int(tokens[2]) - prev + 1
                prev = int(tokens[2]) + 1
        return result