## LeetCode – Power of Four (Java)

Given an integer (signed 32 bits), write a function to check whether it is a power of 4. Java Solution 1 – Naive Iteration public boolean isPowerOfFour(int num) { while(num>0){ if(num==1){ return true; }   if(num%4!=0){ return false; }else{ num=num/4; } }   return false; }public boolean isPowerOfFour(int num) { while(num>0){ if(num==1){ return true; } … Read more

## LeetCode – Reverse Vowels of a String (Java)

Write a function that takes a string as input and reverse only the vowels of a string. Java Solution this is a simple problem which can be solved by using two pointers scanning from beginning and end of the array. public String reverseVowels(String s) { ArrayList<Character> vowList = new ArrayList<Character>(); vowList.add(’a’); vowList.add(’e’); vowList.add(’i’); vowList.add(’o’); vowList.add(’u’); … Read more

## LeetCode – Integer Break (Java)

Given a positive integer n, break it into the sum of at least two positive integers and maximize the product of those integers. Return the maximum product you can get. For example, given n = 2, return 1 (2 = 1 + 1); given n = 10, return 36 (10 = 3 + 3 + … Read more

## LeetCode – Coin Change (Java)

Given a set of coins and a total money amount. Write a method to compute the smallest number of coins to make up the given amount. If the amount cannot be made up by any combination of the given coins, return -1.

For example:
Given [2, 5, 10] and amount=6, the method should return -1.
Given [1, 2, 5] and amount=7, the method should return 2.