[leetcode javascript解题]Multiply Strings

谁践踏了优雅 2022-07-13 09:51 132阅读 0赞

leetcode 第43题“Multiply Strings”描述如下：

> Given two numbers represented as strings, return multiplication of the numbers as a string.  
> Note:  
> The numbers can be arbitrarily large and are non-negative.  
> Converting the input string to integer is NOT allowed.  
> You should NOT use internal library such as BigInteger.

题目就是通过字符串实现大数乘法。关键是把握好进位问题，我代码的思路比较清晰，但是略显繁琐。还有改进的地方：

/** * @param {string} num1 * @param {string} num2 * @return {string} */
    var multiply = function(num1, num2) {
        var result = [],
            temp, l1 = num1.length,
            l2 = num2.length,
            resultStr = "";
        for (var i = l1 - 1; i >= 0; i--) {
            for (var j = l2 - 1; j >= 0; j--) {
                temp = num1[i] * num2[j];
                var tenTemp = Math.floor(temp / 10),
                    oneTemp = Math.floor(temp % 10);
                result[l1 + l2 - i - j - 1] = result[l1 + l2 - i - j - 1] + oneTemp || oneTemp; //个位储存
                result[l1 + l2 - i - j] = result[l1 + l2 - i - j] + tenTemp || tenTemp; //十位储存
            }
        }
        for (i = 1; i < result.length; i++) {
            if (result[i] >= 10) { //进位
                result[i + 1] += Math.floor(result[i] / 10);
                result[i] = Math.floor(result[i] % 10);
            }
        }
        for (j = result.length - 1; j > 0; j--) { //将数组转为字符串
            resultStr += result[j];
        }
        var index = 0;
        while (resultStr[index] === "0") {
            index++;
        }
        return resultStr.substr(index) === "" ? "0" : resultStr.substr(index);
    };