packageeasy;

publicclassZigZagConversion {

publicStringconvert(Strings,intnumRows) {

StringBuilder[]sb =newStringBuilder[numRows];

char[]c=s.toCharArray();

intlen =s.length();

for(inti =0;i <numRows;i++){

sb[i] =newStringBuilder();//this is an important step to initialize it

}

inti =0;

while(i <len){

for(intindex =0;index <numRows &&i <len;index++){

sb[index].append(c[i++]);// vertically down

}

for(intindex =numRows -2;index >=1 &&i <len;index--){/**Why it should start from numRows - 2? Think of the example when numRows = 3

sb[index].append(c[i++]);// obliquely up

}

}

for(i =1;i <numRows;i++){

sb[0].append(sb[i]);

}

returnsb[0].toString();

}

}

|9|[Palindrome Number](https://leetcode.com/problems/palindrome-number/)|[Solution](../../blob/master/EASY/src/easy/PalindromeNumber.java)| O(logn)/(n) | O(1) | Easy

|8|[String to Integer (atoi)](https://leetcode.com/problems/string-to-integer-atoi/)|[Solution](../../blob/master/EASY/src/easy/StringToInteger.java)| O(n) | O(1) | Easy

|7|[Reverse Integer](https://leetcode.com/problems/reverse-integer/)|[Solution](../../blob/master/EASY/src/easy/ReverseInteger.java)| O(1)| O(1)| Easy|

|6|[ZigZag Conversion](https://leetcode.com/problems/zigzag-conversion/)|[Solution](../../blob/master/EASY/src/easy/ZigZagConversion.java)| O(n)| O(n)| Easy|

|2|[Add Two Numbers](https://leetcode.com/problems/add-two-numbers/)|[Solution](../../blob/master/MEDIUM/src/medium/AddTwoNumbers.java) | O(n) | O(1) | Medium | LinkedList

|1|[Two Sum](https://leetcode.com/problems/two-sum/)|[Solution](../../blob/master/EASY/src/easy/TwoSum.java)| O(n)/O(n^2)|O(1)/O(n) | Easy| HashMap