大数加法 Java

import java.util.*;


public class Solution {
    
    public String solve(String s, String t) {
        StringBuilder sb = new StringBuilder();
        int i = s.length() - 1, j = t.length() - 1, carry = 0;
        while (i >= 0 || j >= 0 || carry != 0) {
            int x = i < 0 ? 0 : s.charAt(i--) - '0';
            int y = j < 0 ? 0 : t.charAt(j--) - '0';
            int sum = x + y + carry;
            sb.insert(0, sum % 10);
            carry = sum / 10;
        }
        return sb.toString();
    }
}

import java.util.*;

public class Solution {
    
    public String solve(String s, String t) {
        // write code here
        StringBuilder sb = new StringBuilder();
        int i = s.length() - 1, j = t.length() - 1, carry = 0;
        while (i >= 0 || j >= 0 || carry != 0) {
            int x = i < 0 ? 0 : s.charAt(i--) - '0';
            int y = j < 0 ? 0 : t.charAt(j--) - '0';
            int sum = x + y + carry;
            sb.append(sum % 10);
            carry = sum / 10;
        }
        return sb.reverse().toString();
    }
}

import java.util.*;


public class Solution {
    
    public String solve(String s, String t) {
        Stack stack = new Stack<>();
        StringBuilder sb = new StringBuilder();
        int i = s.length() - 1, j = t.length() - 1, carry = 0;
        while (i >= 0 || j >= 0 || carry != 0) {
            carry += i >= 0 ? s.charAt(i--) - '0' : 0;
            carry += j >= 0 ? t.charAt(j--) - '0' : 0;
            stack.push(carry % 10);
            carry /= 10;
        }
        while (!stack.isEmpty()) {
            sb.append(stack.pop());
        }
        return sb.toString();
    }
}