leetcode-415-Add-Strings

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描述

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

Note:

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

分析

解决方案1(Java)

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class Solution {
    public String addStrings(String num1, String num2) {
        int i = num1.length() - 1, j = num2.length() - 1, carry = 0;
        String result = "";
        while (i >= 0 || j >= 0) {
            if (i >= 0) {
                carry += num1.charAt(i) - '0';
                i--;
            }
            if (j >= 0) {
                carry += num2.charAt(j) - '0';
                j--;
            }
            result = Integer.toString(carry % 10) + result;
            carry /= 10;
        }
        return carry != 0 ? "1" + result: result;
    }
}

解决方案2（Golang）

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func addStrings(num1 string, num2 string) string {
    carry := 0
    result := ""
    
    for i, j := len(num1)-1, len(num2)-1; i >= 0 || j >= 0 || carry !=0; {
        var x, y int
        if i >= 0 {
            x += int(num1[i] - '0')
        }
        if j >= 0 {
            y += int(num2[j] - '0')
        }
        now := x + y + carry
        result = strconv.Itoa(now % 10) + result
        carry = now / 10
        i--
        j--
    }
    return result
}

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