add-strings.md

415. Add Strings - 字符串相加

Tags - 题目标签

Description - 题目描述

EN:

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

You must solve the problem without using any built-in library for handling large integers (such as BigInteger). You must also not convert the inputs to integers directly.

 

Example 1:

Input: num1 = "11", num2 = "123"
Output: "134"

Example 2:

Input: num1 = "456", num2 = "77"
Output: "533"

Example 3:

Input: num1 = "0", num2 = "0"
Output: "0"

 

Constraints:

• 1 <= num1.length, num2.length <= 104
• num1 and num2 consist of only digits.
• num1 and num2 don't have any leading zeros except for the zero itself.

ZH-CN:

给定两个字符串形式的非负整数 num1 和num2 ，计算它们的和并同样以字符串形式返回。

你不能使用任何內建的用于处理大整数的库（比如 BigInteger）， 也不能直接将输入的字符串转换为整数形式。

 

示例 1：

输入：num1 = "11", num2 = "123"
输出："134"

示例 2：

输入：num1 = "456", num2 = "77"
输出："533"

示例 3：

输入：num1 = "0", num2 = "0"
输出："0"

 

 

提示：

• 1 <= num1.length, num2.length <= 104
• num1 和num2 都只包含数字 0-9
• num1 和num2 都不包含任何前导零

Link - 题目链接

LeetCode - LeetCode-CN

Latest Accepted Submissions - 最近一次 AC 的提交

Language	Runtime	Memory	Submission Time
javascript	108 ms	36.1 MB	2020/03/23 17:40

/**
 * @param {string} num1
 * @param {string} num2
 * @return {string}
 */
var addStrings = function(num1, num2){
    //取两个数字的最大长度
    let maxLength = Math.max(num1.length, num2.length);
    //用0去补齐长度
    num1= num1.padStart(maxLength , 0);//"0009007199254740991"
    num2= num2.padStart(maxLength , 0);//"1234567899999999999"
    //定义加法过程中需要用到的变量
    let t = 0;   // 本位的和
    let f = 0;   //"进位"
    let sum = "";
    for(let i= maxLength-1; i>=0 ; i--) {
        t = parseInt(num1[i]) + parseInt(num2[i]) + f;
        f = Math.floor(t/10); // 进位
        sum = t%10 + sum; // 本位字符串加上后面的字符串
    }
    // 最后如果还有进位
    if(f){
        sum = f + sum;
    }
    return sum;
}

My Notes - 我的笔记

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