Map, Set, Priority Queue(우선순위 큐)를 익히는 문제들 추출 ### Silver - [x] <a href="https://www.acmicpc.net/problem/14425" target="_blank">문자열 집합</a> - [x] <a href="https://www.acmicpc.net/problem/2075" target="_blank">N번째 큰 수</a> - [x] <a href="https://www.acmicpc.net/problem/4358" target="_blank">생태학</a> ### Gold - [x] <a href="https://www.acmicpc.net/problem/7662" target="_blank">이중 우선순위 큐</a> - [x] <a href="https://www.acmicpc.net/problem/2696" target="_blank">중앙값 구하기</a> - [ ] <a href="https://www.acmicpc.net/problem/21939" target="_blank">문제 추천 시스템 Version 1</a>
