Employee Importance

题目
You are given a data structure of employee information, which includes the employee's unique id, his importance value and his direct subordinates' id.

For example, employee 1 is the leader of employee 2, and employee 2 is the leader of employee 3. They have importance value 15, 10 and 5, respectively. Then employee 1 has a data structure like [1, 15, [2]], and employee 2 has [2, 10, [3]], and employee 3 has [3, 5, []]. Note that although employee 3 is also a subordinate of employee 1, the relationship is not direct.

Now given the employee information of a company, and an employee id, you need to return the total importance value of this employee and all his subordinates.

答案

class Solution {
    public int getImportance(List employees, int id) {
        Stack stk = new Stack<>();
        Map map = new HashMap<>();
        
        stk.push(id);
        int importance = 0, i = 0;
        for(Employee emp : employees)
            map.put(emp.id, i++);
        
        while(!stk.isEmpty()) {
            int index = map.get(stk.pop());
            Employee emp = employees.get(index);
            importance += emp.importance;
            
            for(int sub : emp.subordinates) {
                stk.push(sub);
            }
        }
        return importance;
    }
}