Multiply Strings

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The key to do this problem is to approach it as you would any multiplication by paper and pencil. Split the strings into characters and continue with the operations.

Full Solution in Java:

 public class Solution {
 public String multiply(String num1, String num2) {

        
        int[] nums=new int[num1.length()+num2.length()];
        
        for (int i=0; i< num2.length(); i++){
            
            int carry=0;
            int a=num2.charAt(num2.length()-i-1)-'0';
            
            for (int j=0; j< num1.length(); j++){
                
                int b=num1.charAt(num1.length()-1-j)-'0';
                
                nums[i+j]+=(a*b)+carry;
                
                carry=nums[i+j]/10;
                nums[i+j]%=10;
                
            }
            nums[i+num1.length()]+=carry;
        }
        
        StringBuffer result=new StringBuffer();
        int i=nums.length-1;

        while(i> 0 && nums[i]==0){
            i--;
        }
        
        while(i >=0){
            result.append(nums[i]);
            i--;
        }
        
        return result.toString();
        
    }
}