From f5fc6baddca9af176b77648229ae26fd4bae137e Mon Sep 17 00:00:00 2001
From: meifannao <meifannao549@163.com>
Date: Sun, 25 Feb 2024 22:12:35 +0800
Subject: [PATCH] =?UTF-8?q?0647.=E5=9B=9E=E6=96=87=E5=AD=90=E4=B8=B2?=
 =?UTF-8?q?=E6=B7=BB=E5=8A=A0Golang=E7=9A=84=E5=8F=8C=E6=8C=87=E9=92=88?=
 =?UTF-8?q?=E8=A7=A3=E6=B3=95?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 problems/0647.回文子串.md | 42 +++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/problems/0647.回文子串.md b/problems/0647.回文子串.md
index d94d18c5..4887ff83 100644
--- a/problems/0647.回文子串.md
+++ b/problems/0647.回文子串.md
@@ -397,6 +397,7 @@ class Solution:
 ```
 
 ### Go：
+> 动态规划：
 
 ```Go
 func countSubstrings(s string) int {
@@ -422,6 +423,47 @@ func countSubstrings(s string) int {
     return res
 }
 ```
+> 动态规划：简洁版
+```Go
+func countSubstrings(s string) int {
+	res := 0
+	dp := make([][]bool, len(s))
+	for i := 0; i < len(s); i++ {
+		dp[i] = make([]bool, len(s))
+	}
+
+	for i := len(s) - 1; i >= 0; i-- {
+		for j := i; j < len(s); j++ {
+			if s[i] == s[j] && (j-i <= 1 || dp[i+1][j-1]) {
+				res++
+				dp[i][j] = true
+			}
+		}
+	}
+	return res
+}
+```
+
+> 双指针法：
+```Go
+func countSubstrings(s string) int {
+	extend := func(i, j int) int {
+		res := 0
+		for i >= 0 && j < len(s) && s[i] == s[j] {
+			i --
+			j ++
+			res ++
+		}
+		return res
+	}
+	res := 0
+	for i := 0; i < len(s); i++ {
+		res += extend(i, i)  // 以i为中心
+		res += extend(i, i+1) // 以i和i+1为中心
+	}
+	return res
+}
+```
 
 ### Javascript：