# 原创：JavaScript 获取版本差值

# 题目

比较版本号 如果 version1 > version2 返回 1，如果 version1 < version2 返回 -1，不然返回 0.

输入的 version 字符串非空，只包含数字和字符.。.字符不代表通常意义上的小数点，只是用来区分数字序列。例如字符串 2.5 并不代表二点五，只是代表版本是第一级版本号是 2，第二级版本号是 5.

示例 1 输入

"0.1","1.1"

输出

-1

# 题目详解

思路 1：第一个点 x 1、第二个点 x 10、第三个 x 100,这个思路是错误的。

思路 2：把 . 当做小数点,注意：这里并非 100% 按照题目要求实现 符号

  • 核心：拉平最大的数组长度 - 缺点：未能解决进制借位的问题
/**
 * 比较版本号
 * @param version1 string字符串
 * @param version2 string字符串
 * @return int整型
 */
function compare(version1, version2) {
  let left = version1.split(".");
  let right = version2.split(".");
  let len = 0;

  console.log(left, right);

  if (left.length > right.length) {
    len = left.length;
    // right fill
    const le = left.length - right.length;
    right = right.concat(Array(le).fill("0"));
  } else if (left.length < right.length) {
    // right fill
    const le = right.length - left.length;
    left = left.concat(Array(le).fill("0"));
    len = right.length;
  } else len = left.length;

  let leftCount = left.reduce((a, b) => a + b);
  let rightCount = right.reduce((a, b) => a + b);

  const diff = rightCount - leftCount;
  const countLen = (diff + "").length;
  const countArray = Array(len).fill("0");
  for (let i = 0; i < countLen; i++) {
    const diffStr = diff + "";
    countArray[len - 1 - i] = diffStr[i];
  }
  const ret = "-" + countArray.join(".");
  return ret;
}

console.log(compare("0.1", "1.1"));
console.log(compare("1.1", "1.11.1"));
// compare("1.1.1", "1.2");

思路 3：借鉴思路 2 的基础，上做了借位出来，并通过了测试用例

// 可在根目录上执行
npm run test

具体的代码实现：

/**
 * 比较版本号
 * @param version1 string字符串
 * @param version2 string字符串
 * @return string
 */
function compare(version1, version2) {
  let left = version1.split("."); // [0,1]
  let right = version2.split("."); // [1.1]
  let len = 0;

  console.log(left, right);

  if (left.length > right.length) {
    len = left.length;
    // right fill
    const le = left.length - right.length;
    right = right.concat(Array(le).fill("0"));
  } else if (left.length < right.length) {
    // right fill
    const le = right.length - left.length;
    left = left.concat(Array(le).fill("0"));
    len = right.length;
  } else len = left.length;
  const arrayData = [];
  let decimal = 0; // 十进制借位
  for (let i = len - 1; i > -1; i--) {
    let rightItem = right[i];
    const leftItem = left[i];
    let diff = 0;
    /**
     *   [1, 11, 0]
     * - [1, 0 , 1]
     * ------------------
     * = [0, 10, 9]
     */
    // decimal handler
    if (rightItem + decimal < leftItem) {
      rightItem = rightItem + decimal + 10;
      diff = rightItem - leftItem;
      decimal = 1;
    } else {
      diff = rightItem - decimal - leftItem;
      decimal = 0;
    }
    arrayData.push(diff);
  }

  // console.log("arrayData========>", arrayData);
  return arrayData.reverse().join(".");
}

本题目用到的测试用例：

const compare = require("../examples/get-version-number");

describe("get-version-number", () => {
  it("version 0.1 -> 1.1 = 1.0", () => {
    expect(compare("0.1", "1.1")).toBe("1.0");
  });

  it("version 1.1 -> 1.1.1 = 0.0.1", () => {
    expect(compare("1.1", "1.1.1")).toBe("0.0.1");
  });

  it("version 1.0.1 -> 1.11 = 0.10.9", () => {
    expect(compare("1.0.1", "1.11")).toBe("0.10.9");
  });
});

# 结尾