2017-12-23 16:40:02 +0000   |     algorithm leetcode dynamic programming   |   Viewed times   |    

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.

Example 1:

Input: [[1, 5, [2, 3]], [2, 3, []], [3, 3, []]], 1
Output: 11
Explanation:
Employee 1 has importance value 5, and he has two direct subordinates: employee 2 and employee 3. They both have importance value 3. So the total importance value of employee 1 is 5 + 3 + 3 = 11.

Note:

自底向上递归动态规划

标准的顺藤摸瓜。从目标员工开始,遍历所有它的直系和非直系下属。这种问题用递归很简单。开始之前把List变成按id索引的Map可以减少搜索的复杂度。

代码

/*
// Employee info
class Employee {
    // It's the unique id of each node;
    // unique id of this employee
    public int id;
    // the importance value of this employee
    public int importance;
    // the id of direct subordinates
    public List<Integer> subordinates;
};
*/
class Solution {
    public int getImportance(List<Employee> employees, int id) {
        return dp(getMap(employees),id);
    }
    private Map<Integer,Employee> getMap(List<Employee> employees) {
        Map<Integer,Employee> map = new HashMap<>();
        for (Employee employee : employees) {
            map.put(employee.id,employee);
        }
        return map;
    }
    private int dp(Map<Integer,Employee> map, int target) {
        Employee e = map.get(target);
        int res = e.importance;
        for (Integer i : e.subordinates) {
            res += dp(map,i);
        }
        return res;
    }
}

结果

employee-importance-1