Function Exclusive Time Calculation

Approach

Functions executing in time order form a call stack structure. This means we can solve it by simulating function calls with a simple stack implementation following the problem description. The main challenge lies in calculating the time spent correctly—just read the requirements carefully.

Solution

#include <sstream>

using namespace std;

class Solution {
public:
    vector<int> exclusiveTime(int n, vector<string>& logs) {
        vector<int> res(n, 0);
        stack<pair<int, int>> st;
        string sno;
        string state;
        string time;
        int id;
        int t;
        
        for(string s : logs) {
            // Split log string
            stringstream ss (s);
            getline(ss, sno, ':');
            getline(ss, state, ':');
            getline(ss, time, ':');
            
            id = stoi(sno);
            t = stoi(time);
            
            if (state == "start") {
                // Start call, push to stack
                st.push(make_pair(id, t));
            } else {
                auto p = st.top();
                st.pop();
                // Start is the head of that moment, end is the tail of finish moment
                t = t - p.second + 1;
                res[p.first] += t;
                
                // Upper function time needs to subtract inner running function time
                if (!st.empty())
                    res[st.top().first]-=t;
            }
        }
        
        return res;
    }
};

Key Takeaways

This exercise reinforces basic STL string operations and stack-based function call simulation techniques.

#stack #string

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