js实现字符串中找最大的回文子串

回文串就是正着读和倒过来读字符的顺序是一样的，字符串中找最大的回文子串，我这里有两种方法来寻找。

方法一：找出字符串的所有子串，判断子串是否是回文串

function findPalindrome () {
      let arr1 = 'asdfgfdsgh'
      let self = this
      let result = ''
      for (let i = 0; i < arr1.length; i++) {
        // let count = 0
        for (let j = arr1.length - 1; j > -1; j--) {
          if (self.isPalindrome(arr1.slice(i, j))) {
            if (result.length < arr1.slice(i, j).length) {
              result = arr1.slice(i, j)
            }
          }
        }
      }
      console.log(result)
      return result
    },
    // 判断一个数是不是回文数
    isPalindrome (str) {
      for (let i = 0; i < str.length; i++) {
        if (str.charAt(i) === str.charAt(str.length - i - 1)) {
          if (i > str.length - i - 1) {
            return true
          }
        } else {
          return false
        }
      }
    }

方法二：给原数组中添加#，遍历该数组，找不到回文串就break，找下一个

isPalindrome () {
      // let str = 'asdfgfdsgh'
      let temp = '#a#s#d#f#g#f#d#s#g#h#'
      // let temp = '#a#a#a#a#a#a#a#a#a#'
      let arr = []
      let result = ''
      for (let i = 1; i < temp.length; i++) {
        arr.push(0)
      }
      for (let i = 1; i < temp.length; i++) {
        let count = 0
        let left = i - 1
        let right = i + 1
        while (left > -1 && right < temp.length) {
          if (temp.charAt(left) === temp.charAt(right)) {
            count++
            left--
            right++
          } else {
            break
          }
        }
        arr[i] = count
      }
      console.log(arr)
      let max = 0
      let inde = 0
      for (let i = 1; i < arr.length; i++) {
        if (arr[i] > max) {
          max = arr[i]
          inde = i
        }
      }
      result = temp.slice(inde - max, inde + max)
      console.log(result)
      result = result.replace(/#/g, '')
      console.log(result)
      return result
    }