[프로그래머스] Lv.1 완주하지 못한 선수 [Python, Java]

• 문제 : https://school.programmers.co.kr/learn/courses/30/lessons/42576
• 해시 함수, 딕셔너리, 해시 맵

파이썬

def solution(participant, completion):
    hashDict={}
    sumHash=0
    
    for name in participant:
        hashDict[hash(name)]=name
        sumHash+=hash(name)

    for name in completion:
        sumHash-=hash(name)
        
    return hashDict[sumHash]

자바

import java.util.*;

class Solution {
    public String solution(String[] participant, String[] completion) {
        Map<String, Integer> map = new HashMap<>();
        
        for (String name : participant) {
            if (map.keySet().contains(name)) {
                map.put(name, map.get(name)+1);
            } else {
                map.put(name, 1);
            } 
        }
        for (String name : completion) {
            if (map.get(name) == 1) {
                map.remove(name);
            } else {
                map.replace(name, map.get(name)-1);
            }
        }

        return map.keySet().iterator().next();
    }
}