On a single-threaded CPU, we execute a program containing n functions. Each function has a unique ID between 0 and n-1.
Function calls are stored in a call stack: when a function call starts, its ID is pushed onto the stack, and when a function call ends, its ID is popped off the stack. The function whose ID is at the top of the stack is the current function being executed. Each time a function starts or ends, we write a log with the ID, whether it started or ended, and the timestamp.
You are given a list logs, where logs[i] represents the ith log message formatted as a string "{function_id}:{"start" | "end"}:{timestamp}". For example, "0:start:3" means a function call with function ID 0 started at the beginning of timestamp 3, and "1:end:2" means a function call with function ID 1 ended at the end of timestamp 2. Note that a function can be called multiple times, possibly recursively.
A function's exclusive time is the sum of execution times for all function calls in the program. For example, if a function is called twice, one call executing for 2 time units and another call executing for 1 time unit, the exclusive time is 2 + 1 = 3.
Return the exclusive time of each function in an array, where the value at the ith index represents the exclusive time for the function with ID i.
just a hashmap? Map the id : start - last start -> accumulate timer. So just for loop the logs, and for the start we record the time and id. For the end, we calculate the cur - last and add it to the result. Then we need to keep running the application before...So this is a stack.
- Use a stack to store the id and start time
- For each log, if it is start, push the id and start time to the stack
- If it is end, pop the stack and calculate the time and add it to the result. Then update the last time to the current time + 1
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Time complexity:
$$O(N)$$ -
Space complexity:
$$O(N)$$