package com.leetcode.string; public class BigNum { public String solve (String s, String t) { StringBuilder sb = new StringBuilder(); int i=s.length()-1,j=t.length()-1; int bit =0; int m=0,n=0,sum=0; while (i>=0||j>=0){ sum=0; if(i>=0){ m = s.charAt(i) - '0'; sum+=m; i--; } if(i>=0){ n = t.charAt(j) - '0'; sum+=n; j--; } sum +=bit; sb.append(sum % 10); bit = sum/10; } return sb.reverse().toString(); } }