Add solution 647

leetcode/0647.Palindromic-Substrings/647. Palindromic Substrings.go

@@ -0,0 +1,23 @@
+package leetcode
+
+func countSubstrings(s string) int {
+	res := 0
+	for i := 0; i < len(s); i++ {
+		res += countPalindrome(s, i, i)
+		res += countPalindrome(s, i, i+1)
+	}
+	return res
+}
+
+func countPalindrome(s string, left, right int) int {
+	res := 0
+	for left >= 0 && right < len(s) {
+		if s[left] != s[right] {
+			break
+		}
+		left--
+		right++
+		res++
+	}
+	return res
+}

leetcode/0647.Palindromic-Substrings/647. Palindromic Substrings_test.go

@@ -0,0 +1,47 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question647 struct {
+	para647
+	ans647
+}
+
+// para 是参数
+// one 代表第一个参数
+type para647 struct {
+	s string
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans647 struct {
+	one int
+}
+
+func Test_Problem647(t *testing.T) {
+
+	qs := []question647{
+
+		{
+			para647{"abc"},
+			ans647{3},
+		},
+
+		{
+			para647{"aaa"},
+			ans647{6},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 647------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans647, q.para647
+		fmt.Printf("【input】:%v       【output】:%v\n", p, countSubstrings(p.s))
+	}
+	fmt.Printf("\n\n\n")
+}

leetcode/0647.Palindromic-Substrings/README.md

@@ -0,0 +1,64 @@
+# [647. Palindromic Substrings](https://leetcode.com/problems/palindromic-substrings/)
+
+
+## 题目
+
+Given a string, your task is to count how many palindromic substrings in this string.
+
+The substrings with different start indexes or end indexes are counted as different substrings even they consist of same characters.
+
+**Example 1:**
+
+```
+Input: "abc"
+Output: 3
+Explanation: Three palindromic strings: "a", "b", "c".
+```
+
+**Example 2:**
+
+```
+Input: "aaa"
+Output: 6
+Explanation: Six palindromic strings: "a", "a", "a", "aa", "aa", "aaa".
+```
+
+**Note:**
+
+1. The input string length won't exceed 1000.
+
+## 题目大意
+
+给定一个字符串，你的任务是计算这个字符串中有多少个回文子串。具有不同开始位置或结束位置的子串，即使是由相同的字符组成，也会被视作不同的子串。
+
+## 解题思路
+
+- 暴力解法，从左往右扫一遍字符串，以每个字符做轴，用中心扩散法，依次遍历计数回文子串。
+
+## 代码
+
+```go
+package leetcode
+
+func countSubstrings(s string) int {
+	res := 0
+	for i := 0; i < len(s); i++ {
+		res += countPalindrome(s, i, i)
+		res += countPalindrome(s, i, i+1)
+	}
+	return res
+}
+
+func countPalindrome(s string, left, right int) int {
+	res := 0
+	for left >= 0 && right < len(s) {
+		if s[left] != s[right] {
+			break
+		}
+		left--
+		right++
+		res++
+	}
+	return res
+}
+```