1. is palindrome
solution 1: check to reverse the digit, if they are the same number https://www.geeksforgeeks.org/write-a-c-program-to-reverse-digits-of-a-number/
solution 2: change int to String in java and compare it
check geekforgeek and leetcode for more solutions, recurseive
2. kth largest number
quick sort or priority queue
原文：https://www.cnblogs.com/stiles/p/geekforgeek1.html