【牛客题霸题解】大数相加

先反转，再相加，过程中记录一下进位
c++

class Solution {
public:
    string solve(string s, string t) {
        reverse(s.begin(),s.end());
        reverse(t.begin(),t.end());
        string ans = "";
        int len = max(s.length(),t.length());
        int d = 0;//记录进位
        for(int i = 0 ; i < len ; i++)
        {
            int si= 0,ti = 0;
            if(i<s.length()){
                si = s[i]-'0';
            }
            if(i<t.length()){
                ti = t[i]-'0';
            }
            ans+=(si+ti+d)%10+'0';
            d = (si+ti+d)/10;
        }
        if(d) { ans+=d+'0'; }
        reverse(ans.begin(),ans.end());
        return ans;
    }
};

java

import java.util.*;
public class Solution {
    public String solve (String s, String t) {
        StringBuffer s1 =new StringBuffer(s);
        s1 = s1.reverse();
        StringBuffer t1 =new StringBuffer(t);
        t1 = t1.reverse();
        StringBuffer ans =new StringBuffer();
        int len = Math.max(s.length(),t.length());
        int d = 0;//记录进位
        for(int i = 0 ; i < len ; i++)
        {
            int si= 0,ti = 0;
            if(i<s.length()){
                si = s1.charAt(i)-'0';
            }
            if(i<t.length()){
                ti = t1.charAt(i)-'0';
            }
            ans.append((char)((si+ti+d)%10+'0'));
            d = (si+ti+d)/10;
        }
        if(d>0) { ans.append((char)(d+'0'));}
        return ans.reverse().toString();
    }
}

python

class Solution:
    def solve(self , s , t ):
        s = s[::-1]
        t = t[::-1]
        ans = ''
        length = max(len(s),len(t));
        #记录进位
        d = 0
        for i in range(length):
            si = 0
            ti = 0
            if i<len(s):
                si = int(s[i])
            if i<len(t):
                ti = int(t[i])
            ans += str((si+ti+d)%10)
            d = (si+ti+d)//10
        if d>0:
           ans += str(d)
        return ans[::-1]

java和python语言里其实是自带高精度实现的
java

import java.util.*;
import java.math.BigInteger;
public class Solution {
    public String solve (String s, String t) {
        BigInteger S = new BigInteger(s);
        BigInteger T = new BigInteger(t);
        return S.add(T).toString();
    }
}

python

class Solution:
    def solve(self , s , t ):
        return int(s)+int(t)