Add Strings

描述

Given two non-negative integers num1 and num2 represented as string, return the sum of num1 and num2.

Note:

• The length of both num1 and num2 is < 5100.
• Both num1 and num2 contains only digits 0-9.
• Both num1 and num2 does not contain any leading zero.
• You must not use any built-in BigInteger library or convert the inputs to integer directly.

分析

这题与 Add Binary 一模一样，将它的代码中的 2 改为 10 即可。

代码

Java

// Add Strings
// Time Complexity: O(max(m,n)), Space Complexity: O(max(m,n))
class Solution {
    public String addStrings(String num1, String num2) {
        StringBuilder result = new StringBuilder();
        int i = num1.length() - 1, j = num2.length() - 1, carry = 0;
        while(i >= 0 || j >= 0 || carry > 0) {
            int x = i < 0 ? 0 : num1.charAt(i--) - '0';
            int y = j < 0 ? 0 : num2.charAt(j--) - '0';
            int sum = x + y + carry;
            result.append(sum % 10);
            carry = sum / 10;
        }
        return result.reverse().toString();
    }
};

C++

// Add Strings
// Time Complexity: O(max(m,n)), Space Complexity: O(max(m,n))
class Solution {
public:
    string addStrings(string num1, string num2) {
        string result;
        int i = num1.length() - 1, j = num2.length() - 1, carry = 0;

        while(i >= 0 || j >= 0 || carry > 0) {
            int x = i < 0 ? 0 : num1[i--] - '0';
            int y = j < 0 ? 0 : num2[j--] - '0';
            int sum = x + y + carry;
            result.insert(result.begin(), (sum % 10) + '0');
            carry = sum / 10;
        }
        return result;
    }
};

相关题目

• Add Two Numbers
• Add Binary
• Multiply Strings