636. Exclusive Time of Functions

Description

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.

 

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 the beginning of time 0, then it executes 2 for units of time and reaches the end of time 1.
Function 1 starts at the beginning of time 2, executes for 4 units of time, and ends at the end of time 5.
Function 0 resumes execution at the beginning of time 6 and executes for 1 unit of time.
So function 0 spends 2 + 1 = 3 units of total time executing, and function 1 spends 4 units of total time executing.

Example 2:

Input: n = 1, logs = ["0:start:0","0:start:2","0:end:5","0:start:6","0:end:6","0:end:7"]
Output: [8]
Explanation:
Function 0 starts at the beginning of time 0, executes for 2 units of time, and recursively calls itself.
Function 0 (recursive call) starts at the beginning of time 2 and executes for 4 units of time.
Function 0 (initial call) resumes execution then immediately calls itself again.
Function 0 (2nd recursive call) starts at the beginning of time 6 and executes for 1 unit of time.
Function 0 (initial call) resumes execution at the beginning of time 7 and executes for 1 unit of time.
So function 0 spends 2 + 4 + 1 + 1 = 8 units of total time executing.

Example 3:

Input: n = 2, logs = ["0:start:0","0:start:2","0:end:5","1:start:6","1:end:6","0:end:7"]
Output: [7,1]
Explanation:
Function 0 starts at the beginning of time 0, executes for 2 units of time, and recursively calls itself.
Function 0 (recursive call) starts at the beginning of time 2 and executes for 4 units of time.
Function 0 (initial call) resumes execution then immediately calls function 1.
Function 1 starts at the beginning of time 6, executes 1 unit of time, and ends at the end of time 6.
Function 0 resumes execution at the beginning of time 6 and executes for 2 units of time.
So function 0 spends 2 + 4 + 1 = 7 units of total time executing, and function 1 spends 1 unit of total time executing.

 

Constraints:

  • 1 <= n <= 100
  • 1 <= logs.length <= 500
  • 0 <= function_id < n
  • 0 <= timestamp <= 109
  • No two start events will happen at the same timestamp.
  • No two end events will happen at the same timestamp.
  • Each function has an "end" log for each "start" log.

Solutions

Solution 1

Python Code
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class Solution:
    def exclusiveTime(self, n: int, logs: List[str]) -> List[int]:
        ans = [0] * n
        stk = []
        curr = -1
        for log in logs:
            t = log.split(':')
            fid = int(t[0])
            ts = int(t[2])
            if t[1] == 'start':
                if stk:
                    ans[stk[-1]] += ts - curr
                stk.append(fid)
                curr = ts
            else:
                fid = stk.pop()
                ans[fid] += ts - curr + 1
                curr = ts + 1
        return ans

Java Code
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class Solution {
    public int[] exclusiveTime(int n, List<String> logs) {
        int[] ans = new int[n];
        Deque<Integer> stk = new ArrayDeque<>();
        int curr = -1;
        for (String log : logs) {
            String[] t = log.split(":");
            int fid = Integer.parseInt(t[0]);
            int ts = Integer.parseInt(t[2]);
            if ("start".equals(t[1])) {
                if (!stk.isEmpty()) {
                    ans[stk.peek()] += ts - curr;
                }
                stk.push(fid);
                curr = ts;
            } else {
                fid = stk.pop();
                ans[fid] += ts - curr + 1;
                curr = ts + 1;
            }
        }
        return ans;
    }
}

C++ Code
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class Solution {
public:
    vector<int> exclusiveTime(int n, vector<string>& logs) {
        vector<int> ans(n);
        stack<int> stk;
        int curr = -1;
        for (auto& log : logs) {
            char type[10];
            int fid, ts;
            sscanf(log.c_str(), "%d:%[^:]:%d", &fid, type, &ts);
            if (type[0] == 's') {
                if (!stk.empty()) ans[stk.top()] += ts - curr;
                curr = ts;
                stk.push(fid);
            } else {
                fid = stk.top();
                stk.pop();
                ans[fid] += ts - curr + 1;
                curr = ts + 1;
            }
        }
        return ans;
    }
};

Go Code
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func exclusiveTime(n int, logs []string) []int {
	ans := make([]int, n)
	stk := []int{}
	curr := 1
	for _, log := range logs {
		t := strings.Split(log, ":")
		fid, _ := strconv.Atoi(t[0])
		ts, _ := strconv.Atoi(t[2])
		if t[1][0] == 's' {
			if len(stk) > 0 {
				ans[stk[len(stk)-1]] += ts - curr
			}
			stk = append(stk, fid)
			curr = ts
		} else {
			fid := stk[len(stk)-1]
			stk = stk[:len(stk)-1]
			ans[fid] += ts - curr + 1
			curr = ts + 1
		}
	}
	return ans
}

TypeScript Code
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function exclusiveTime(n: number, logs: string[]): number[] {
    const res = new Array(n).fill(0);
    const stack: [number, number][] = [];

    for (const log of logs) {
        const t = log.split(':');
        const [id, state, time] = [Number(t[0]), t[1], Number(t[2])];

        if (state === 'start') {
            if (stack.length !== 0) {
                const pre = stack[stack.length - 1];
                res[pre[0]] += time - pre[1];
            }
            stack.push([id, time]);
        } else {
            const pre = stack.pop();
            res[pre[0]] += time - pre[1] + 1;
            if (stack.length !== 0) {
                stack[stack.length - 1][1] = time + 1;
            }
        }
    }

    return res;
}