算法-大数相加

demo

面试中的第一个版本

问题比较多

• 忘记i— j—
• 思路方向对了 但是实现细节不对；太过于绕了，其实可以直接挨着进行加就好了 如果是undefined那就用0来兜底
• 语法比较啰嗦
• Number应该用到每个的上面

亮点

• 双指针大体思路正确
• while循环正确 但实现不对
• unshift和从尾部倒着累加正确

function bigInt(a,b) {
   let aArr = [...a]
   let bArr = [...b]
   let result = []
   let tmp = 0
   let i = aArr.length - 1
   let j = bArr.length - 1
   while (aArr.length && bArr.length) {
       const isGreaterThan10 = Number(aArr[i] + bArr[j] + tmp) > 10
       if (isGreaterThan10) {
           tmp = '1'
       }  else {
           tmp = '0'
       }
       result.unshift(isGreaterThan10 ? aArr[i] + bArr[j] - 10 : aArr[i] + bArr[j])
   }
    let left = []
    if (aArr.length > 0) {
        left = aArr
    } else if (bArr.length > 0) {
        left = bArr
    }
  result = [...left, ...result]
    return result.join('')
    
}

console.log(bigInt('12345678901234567890', '98765432109876543211110'));

下来后自己实现的版本

var addStrings = function(a, b) {
            let aArr = [...a].reverse()
            let bArr = [...b].reverse()
            const maxLen = Math.max(aArr.length, bArr.length)
            let tmp = 0
            let result = []
            for (let i = 0; i < maxLen; i++) {
                const total = (Number(aArr[i]) || 0) + (Number(bArr[i]) || 0) + tmp;
                tmp = Math.floor(total / 10)
                result.unshift(total % 10)
            }

            if (tmp > 0) {
                result.unshift(1)
            }

            return result.join('')

};

官方题解

https://leetcode.cn/problems/add-strings/description/

主要是用到了双指针

var addStrings = function(num1, num2) {
    let i = num1.length - 1, j = num2.length - 1, add = 0;
    const ans = [];
    while (i >= 0 || j >= 0 || add != 0) {
        const x = i >= 0 ? num1.charAt(i) - '0' : 0;
        const y = j >= 0 ? num2.charAt(j) - '0' : 0;
        const result = x + y + add;
        ans.push(result % 10);
        add = Math.floor(result / 10);
        i -= 1;
        j -= 1;
    }
    return ans.reverse().join('');
};