feat: 0005. Longest Palindromic Substring

Author: kimi0230

Leetcode/0005.Longest-Palindromic-Substring/0005.LongestPalindromicString.jpg

@@ -1,9 +1,64 @@
 ---
-title: 0005.Longest Palindromic Substring
-tags: Medium, Dynamic Programming
-author: Kimi Tsai <[email protected]>
-description:
+title: 0005. Longest Palindromic Substring
+subtitle: "https://leetcode.com/problems/remove-nth-node-from-end-of-list/"
+date: 2024-03-23T21:08:00+08:00
+lastmod: 2024-03-23T21:08:00+08:00
+draft: false
+author: "Kimi.Tsai"
+authorLink: "https://kimi0230.github.io/"
+description: "0005. Longest Palindromic Substring"
+license: ""
+images: []
+
+tags: [LeetCode, Go, Medium, DP, Amazon, Microsoft, Google, Adobe, Facebook]
+categories: [LeetCode]
+
+featuredImage: ""
+featuredImagePreview: ""
+
+hiddenFromHomePage: false
+hiddenFromSearch: false
+twemoji: false
+lightgallery: true
+ruby: true
+fraction: true
+fontawesome: true
+linkToMarkdown: false
+rssFullText: false
+
+toc:
+  enable: true
+  auto: true
+code:
+  copy: true
+  maxShownLines: 200
+math:
+  enable: false
+  # ...
+mapbox:
+  # ...
+share:
+  enable: true
+  # ...
+comment:
+  enable: true
+  # ...
+library:
+  css:
+    # someCSS = "some.css"
+    # located in "assets/"
+    # Or
+    # someCSS = "https://cdn.example.com/some.css"
+  js:
+    # someJS = "some.js"
+    # located in "assets/"
+    # Or
+    # someJS = "https://cdn.example.com/some.js"
+seo:
+  images: []
+  # ...
 ---
+
 # [0005.Longest Palindromic Substring](https://leetcode.com/problems/longest-palindromic-substring/)
 
 ## 題目
@@ -34,9 +89,46 @@ Constraints:
 給你一個字符串 s，找到 s 中最長的回文子串。
 
 ## 解題思路
+* 每一個字符本身都是回文
+* 長度為 2, 且首尾字符相同則為回文
+* 長度>=3, 如果頭尾相同, 則去掉頭尾後可看是合是回文. 如果頭尾不同則不是回文
 
+![](0005.LongestPalindromicString.jpg)
 
 ## 來源
 * https://leetcode.com/problems/longest-palindromic-substring/
+* https://leetcode.cn/problems/longest-palindromic-substring/solutions/1348874/s-by-xext-5zk3/
 
 ## 解答
+```go
+package longestpalindromicsubstring
+
+func longestPalindrome(s string) string {
+	dp := make([][]bool, len(s))
+	result := s[0:1]
+
+	for i := 0; i < len(s); i++ {
+		dp[i] = make([]bool, len(s))
+		dp[i][i] = true // 每個字符本身都是回文
+	}
+	for length := 2; length <= len(s); length++ {
+		for start := 0; start < len(s)-length+1; start++ {
+			end := start + length - 1
+			if s[start] != s[end] {
+				// 字頭字尾不同, 不是回文
+				continue
+			} else if length < 3 {
+				// 長度為2且字頭字尾相同, 則為回文
+				dp[start][end] = true
+			} else {
+				// 狀態轉移 : 去掉字頭字尾, 判斷是否還是回文
+				dp[start][end] = dp[start+1][end-1]
+			}
+			if dp[start][end] && (end-start+1) > len(result) {
+				result = s[start : end+1]
+			}
+		}
+	}
+	return result
+}
+```

Leetcode/0005.Longest-Palindromic-Substring/README.md

@@ -1,17 +1,30 @@
 package longestpalindromicsubstring
 
-func LongestPalindromeSubstring(s string) string {
+func longestPalindrome(s string) string {
+	dp := make([][]bool, len(s))
+	result := s[0:1]
 
-	return ""
-}
-
-type numbers interface {
-	int | int8 | int16 | int32 | int64 | float32 | float64
-}
-
-func max[T numbers](a T, b T) T {
-	if a > b {
-		return a
+	for i := 0; i < len(s); i++ {
+		dp[i] = make([]bool, len(s))
+		dp[i][i] = true // 每個字符本身都是回文
+	}
+	for length := 2; length <= len(s); length++ {
+		for start := 0; start < len(s)-length+1; start++ {
+			end := start + length - 1
+			if s[start] != s[end] {
+				// 字頭字尾不同, 不是回文
+				continue
+			} else if length < 3 {
+				// 長度為2且字頭字尾相同, 則為回文
+				dp[start][end] = true
+			} else {
+				// 狀態轉移 : 去掉字頭字尾, 判斷是否還是回文
+				dp[start][end] = dp[start+1][end-1]
+			}
+			if dp[start][end] && (end-start+1) > len(result) {
+				result = s[start : end+1]
+			}
+		}
 	}
-	return b
+	return result
 }

Leetcode/0005.Longest-Palindromic-Substring/main.go

@@ -18,7 +18,7 @@ var tests = []struct {
 
 func TestLongestPalindromeSubstring(t *testing.T) {
 	for _, tt := range tests {
-		if got := LongestPalindromeSubstring(tt.arg1); got != tt.want {
+		if got := longestPalindrome(tt.arg1); got != tt.want {
 			t.Errorf("got = %v, want = %v", got, tt.want)
 		}
 	}
@@ -27,7 +27,7 @@ func TestLongestPalindromeSubstring(t *testing.T) {
 func BenchmarkLongestPalindromeSubstring(b *testing.B) {
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		LongestPalindromeSubstring(tests[0].arg1)
+		longestPalindrome(tests[0].arg1)
 	}
 }
 

Leetcode/0005.Longest-Palindromic-Substring/main_test.go

@@ -0,0 +1,40 @@
+// 時間複雜度:
+// 空間複雜度:
+/*
+ * @lc app=leetcode.cn id=5 lang=golang
+ *
+ * [5] 最长回文子串
+ */
+
+// @lc code=start
+func longestPalindrome(s string) string {
+	dp := make([][]bool, len(s))
+	result := s[0:1]
+
+	for i := 0; i < len(s); i++ {
+		dp[i] = make([]bool, len(s))
+		dp[i][i] = true // 每個字符本身都是回文
+	}
+	for length := 2; length <= len(s); length++ {
+		for start := 0; start < len(s)-length+1; start++ {
+			end := start + length - 1
+			if s[start] != s[end] {
+				// 字頭字尾不同, 不是回文
+				continue
+			} else if length < 3 {
+				// 長度為2且字頭字尾相同, 則為回文
+				dp[start][end] = true
+			} else {
+				// 狀態轉移 : 去掉字頭字尾, 判斷是否還是回文
+				dp[start][end] = dp[start+1][end-1]
+			}
+			if dp[start][end] && (end-start+1) > len(result) {
+				result = s[start : end+1]
+			}
+		}
+	}
+	return result
+}
+
+// @lc code=end
+