https://leetcode.com/problems/count-and-say/description/ My GitHub: Count And Say The nth level result is from counting each digit of the result of (n-1) th level.

# Tag: Coding Interview

## String to Integer (atoi)

https://leetcode.com/problems/string-to-integer-atoi/description/ github: String to Integer(atoi) Checking point: null or empty string white spaces +/- sign calculate real value handle min & max github: String to Integer(atoi) ** trim white space before checking string is empty, so we can ignore whitespaces before number **

## Using StringBuffer solve Reverse Integer problem

LeetCode: https://leetcode.com/problems/reverse-integer/description/ The below Solution 1 is the most popular solution we can find online. But here is another way (Solution 2) to solve the problem with StringBuffer. The Solution 2 is easier to understand and the code is cleaner. Solution 1: Solution 2:

## leetcode- Rotate Image

Leetcode: https://leetcode.com/problems/rotate-image/description/ Given input matrix = [1,2,3], [4,5,6], [7,8,9] rotate the input matrix in-place such that it becomes: [7,4,1], [8,5,2], [9,6,3] (x, y), the affected point is (y, n – x – 1), (n – x – 1, n – y – 1), (n – y – 1, x), “n” is the size of the matrix. … Continue reading leetcode- Rotate Image

## LeetCode – Plus One

Given a non-negative integer represented as a non-empty array of digits, plus one to the integer. You may assume the integer do not contain any leading zero, except the number 0 itself. The digits are stored such that the most significant digit is at the head of the list. For example: Q1. int[] nums = {1,2,3,4}; int[] … Continue reading LeetCode – Plus One

## LeetCode – Two Sum II

Given an array of integers that is already sorted in ascending order, find two numbers such that they add up to a specific target number. CheckPoint: if (numbers != null && numbers.length > 1) {throw new IllegalArgumentException("No solution!");} 1st: 2nd: