NC1题解 | #大数加法#

此题目关键

• 1、字符串判空操作
• 2、字符串长度不一致，补全(取最长)还是截取(取最小)再补
• 3、要用StringBuilder代替String做拼接，节省运行时间

import java.util.*;
public class Solution {
     public static String solve (String s, String t) {
        if(s==null || s.length()==0) {
            return t;
        }
        if(t==null || t.length()==0) {
            return s;
        }
        // write code here
        int maxLen = s.length() > t.length() ? s.length() : t.length();
        int cin = 0;
        int a,b,res;
        String ss = "";
        char[] ch1 = s.toCharArray();
        char[] ch2 = t.toCharArray();
        int[] ch = new int[maxLen+1];
        StringBuilder sb = new StringBuilder();
        for(int i = 1; i <= maxLen; i++){
            if(i<=s.length()) {
                a = ch1[s.length()-i]-'0';
            }else{
                a = 0;
            }
            if(i<=t.length()) {
                b = ch2[t.length()-i]-'0';
            }else{
                b = 0;
            }
            res = a + b + cin;
            if(res>=10){
                res = res -10;
                cin = 1;
            }else{
                cin = 0;
            }
            ch[ch.length-i]=res;
        }
        if(cin>0){
            sb.append(cin);
        }
        for(int i = 1; i < ch.length; i++){
            sb.append(ch[i]);
        }
        return sb.toString();
    }
}