LeetCode-14. Longest Common Prefix

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问题描述

rite a function to find the longest common prefix string amongst an array of strings.

If there is no common prefix, return an empty string "".

Example :

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Input: strs = ["flower","flow","flight"]
Output: "fl"

Constraints:

  • 1 <= strs.length <= 200
  • 0 <= strs[i].length <= 200
  • strs[i] consists of only lower-case English letters.

解答

方法一：横向扫描
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/*
 * @Description: 14. Longest Common Prefix
 * @Author: libk
 * @Github: https://github.com/libk
 */
/**
 * @description: 方法一：横向扫描
 * @param {string[]} strs
 * @return {string}
 */
const longestCommonPrefix = function (strs) {
  const prefixOfTwo = (str1, str2) => {
    const len = Math.min(str1.length, str2.length)
    let index = 0
    while (index < len && str1[index] === str2[index]) {
      index++
    }
    return str1.substring(0, index)
  }

  let prefix = strs[0]
  for (let i = 1; i < strs.length; i++) {
    prefix = prefixOfTwo(prefix, strs[i])
  }
  return prefix
}
方法二：纵向扫描
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/*
 * @Description: 14. Longest Common Prefix
 * @Author: libk
 * @Github: https://github.com/libk
 */
/**
 * @description: 方法二：纵向扫描
 * @param {string[]} strs
 * @return {string}
 */
const longestCommonPrefix = function (strs) {
  const len = strs.length
  const count = strs[0].length

  for (let i = 0; i < count; i++) {
    let first = strs[0][i]
    for (let j = 1; j < len; j++) {
      if (strs[j][i] !== first || i === strs[j].length) {
        return strs[0].substring(0, i)
      }
    }
  }
  return strs[0] 
}