Add Binary Java Solution - The Coding Shala

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Add Binary


Given two binary strings, return their sum (also a binary string).

The input strings are both non-empty and contain only characters 1 or 0.

Example 1:

Input: a = "11", b = "1"
Output: "100"
Example 2:

Input: a = "1010", b = "1011"
Output: "10101"

Add Binary Java Solution


Traverse from backward both string and check carry.


class Solution {
    public String addBinary(String a, String b) {
        String ans = "";
        int len1 = a.length()-1;
        int len2 = b.length()-1;
        if(len1<0 && len2<0) return "0";
        int carry = 0;
        while(len1>=0 || len2>=0){
            int tmp = carry;
            if(len1>=0) tmp += a.charAt(len1)-'0'; //take char as int from a string
            if(len2>=0) tmp += b.charAt(len2)-'0'; //take char as int from b string
            ans = tmp%2 + ans;  //add to new string after adding both char
            carry = tmp/2; //check carry
        if(carry>0) ans = 1+ans; //check carry
        return ans;

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