Kotlin Android leetcode rxjava Algorithm RxJava3 ReactiveX design_pattern rx연산자 rx operator rx_operator RX 디자인패턴 tistory_markdown leetcode876 30-days-challenge algorith 스테이트 패턴 state_pattern 데코레이터패턴 decorator_pattern 반응형프로그래밍 zip() rxjava_scheduler 반응형 프로그래밍 android_rxjava_retrofit Retforit Rxava Android_WorkManager WorkManager leetcode_46 리액티브 프로그래밍 leetcode_338 leetcode_189 material_design bottom_sheet reduce() leetcode419 typora filter() Observable permutation state reactive Markdown Decorator Observer