Go（Golang）中找到字符串中最大回文子串的方法

概述

我们的目标是找到一个字符串中最大的回文子串。例如，我们假设输入的字符串是

cabae

输出应该是aba ，这是最大的回文子串。

我们将使用动态编程来解决这个问题。我们将使用两个矩阵。每个矩阵的大小都是len*len，其中len是输入字符串的大小。

• 第一个矩阵将存储索引**"i "** 和**"j "**之间的子串是否是回文。

• 第二个矩阵将存储**"i "** 和**"j**"之间最长的回文子串**。**

下面是最佳的子结构

• 如果string[i] == string[j]，并且i+1和 j-1中的子串是一个回文，那么

len(i,j) = 2 + len(i+1, j-1)

• 如果string[i] != string[j] 那么

len(i,j) = max(len(i+1,j), len(i,j-1)

程序

以下是相同的程序

package main

import (
	"fmt"
	"math"
	"unicode/utf8"
)

func main() {
	output := longestPalindrome("cabae")
	fmt.Println(output)
}

func longestPalindrome(s string) string {
	stringLength := utf8.RuneCountInString(s)
	isPalindromeMatrix := make([][]int, stringLength)
	for i := range isPalindromeMatrix {
		isPalindromeMatrix[i] = make([]int, stringLength)
	}

	for i, outer := range isPalindromeMatrix {
		for j := range outer {
			if i == j {
				isPalindromeMatrix[i][j] = 1
			}

		}
	}

	palindromeLengthMatrix := make([][]int, stringLength)
	for i := range palindromeLengthMatrix {
		palindromeLengthMatrix[i] = make([]int, stringLength)
	}

	for i, outer := range palindromeLengthMatrix {
		for j := range outer {
			if i == j {
				palindromeLengthMatrix[i][j] = 1
			}

		}
	}

	for len := 2; len <= stringLength; len++ {
		for i := 0; i <= stringLength-len; i++ {
			j := i + len - 1

			if s[i] == s[j] {
				if len == 2 {
					isPalindromeMatrix[i][j] = 1
					palindromeLengthMatrix[i][j] = 2
				} else {
					if isPalindromeMatrix[i+1][j-1] == 1 {
						isPalindromeMatrix[i][j] = 1
						palindromeLengthMatrix[i][j] = 2 + palindromeLengthMatrix[i+1][j-1]
					} else {
						isPalindromeMatrix[i][j] = -1
						palindromeLengthMatrix[i][j] = int(math.Max(float64(palindromeLengthMatrix[i+1][j]), float64(palindromeLengthMatrix[i][j-1])))
					}

				}

			} else {
				isPalindromeMatrix[i][j] = -1
			}

		}
	}

	max_row_index := 0
	max_column_index := 0
	max := 0

	for i, outer := range palindromeLengthMatrix {
		for j := range outer {
			if palindromeLengthMatrix[i][j] > max && isPalindromeMatrix[i][j] == 1 {
				max = palindromeLengthMatrix[i][j]
				max_row_index = i
				max_column_index = j
			}
		}
	}

	return s[max_row_index : max_column_index+1]
}

输出

aba

The postLongest Palindromic Substring within a string in Go (Golang)appeared first onWelcome To Golang By Example.