添加 problem 20

Algorithms/20.Valid Parentheses/README.md

@@ -0,0 +1,57 @@
+# [20. Valid Parentheses](https://leetcode.com/problems/valid-parentheses/description/)
+
+## 题目
+
+Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.
+
+An input string is valid if:
+
+Open brackets must be closed by the same type of brackets.
+Open brackets must be closed in the correct order.
+Note that an empty string is also considered valid.
+
+Example 1:
+
+```
+Input: "()"
+Output: true
+
+```
+
+
+Example 2:
+
+```
+Input: "()[]{}"
+Output: true
+
+```
+
+Example 3:
+
+```
+Input: "(]"
+Output: false
+```
+
+Example 4:
+
+```
+Input: "([)]"
+Output: false
+```
+
+Example 5:
+
+```
+Input: "{[]}"
+Output: true
+```
+
+## 题目大意
+
+括号匹配问题
+
+遇到左括号就进栈push，遇到右括号并且栈顶为与之对应的左括号，就把栈顶元素出栈。最后看栈里面还有没有其他元素，如果为空，即匹配。
+
+需要注意，空字符串是满足括号匹配的，即输出 true。

Algorithms/20.Valid Parentheses/Valid Parentheses.go

@@ -0,0 +1,21 @@
+package leetcode
+
+func isValid(s string) bool {
+	// 空字符串直接返回 true
+	if len(s) == 0 {
+		return true
+	}
+	stack := make([]rune, 0)
+	for _, v := range s {
+		if (v == '[') || (v == '(') || (v == '{') {
+			stack = append(stack, v)
+		} else if ((v == ']') && len(stack) > 0 && stack[len(stack)-1] == '[') ||
+			((v == ')') && len(stack) > 0 && stack[len(stack)-1] == '(') ||
+			((v == '}') && len(stack) > 0 && stack[len(stack)-1] == '{') {
+			stack = stack[:len(stack)-1]
+		} else {
+			return false
+		}
+	}
+	return len(stack) == 0
+}

Algorithms/20.Valid Parentheses/Valid Parentheses_test.go

@@ -0,0 +1,69 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question20 struct {
+	para20
+	ans20
+}
+
+// para 是参数
+// one 代表第一个参数
+type para20 struct {
+	one string
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans20 struct {
+	one bool
+}
+
+func Test_Problem20(t *testing.T) {
+
+	qs := []question20{
+
+		question20{
+			para20{"()[]{}"},
+			ans20{true},
+		},
+		question20{
+			para20{"(]"},
+			ans20{false},
+		},
+		question20{
+			para20{"({[]})"},
+			ans20{true},
+		},
+		question20{
+			para20{"(){[({[]})]}"},
+			ans20{true},
+		},
+		question20{
+			para20{"((([[[{{{"},
+			ans20{false},
+		},
+		question20{
+			para20{"(())]]"},
+			ans20{false},
+		},
+		question20{
+			para20{""},
+			ans20{true},
+		},
+		question20{
+			para20{"["},
+			ans20{false},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 20------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans20, q.para20
+		fmt.Printf("【input】:%v       【output】:%v\n", p, isValid(p.one))
+	}
+}

README.md

@@ -75,7 +75,7 @@
 |17|[Letter Combinations of a Phone Number](./Algorithms/17.letter-combinations-of-a-phone-number)|36%|Medium||
 |18|[4Sum](./Algorithms/18.4sum)|27%|Medium||
 |19|[Remove Nth Node From End of List](./Algorithms/19.remove-nth-node-from-end-of-list)|33%|Medium||
-|20|[Valid Parentheses](./Algorithms/20.valid-parentheses)|33%|Easy||
+|20|[Valid Parentheses](./Algorithms/20.Valid-Parentheses)|33%|Easy||
 |21|[Merge Two Sorted Lists](./Algorithms/21.merge-two-sorted-lists)|41%|Easy||
 |22|[Generate Parentheses](./Algorithms/22.generate-parentheses)|48%|Medium|[❤](https://leetcode.com/list/oussv5j)|
 |23|[Merge k Sorted Lists](./Algorithms/23.merge-k-sorted-lists)|28%|Hard||
@@ -178,7 +178,7 @@
 |122|[Best Time to Buy and Sell Stock II](./Algorithms/122.best-time-to-buy-and-sell-stock-ii)|47%|Easy||
 |123|[Best Time to Buy and Sell Stock III](./Algorithms/123.best-time-to-buy-and-sell-stock-iii)|30%|Hard||
 |124|[Binary Tree Maximum Path Sum](./Algorithms/124.binary-tree-maximum-path-sum)|27%|Hard|[❤](https://leetcode.com/list/oussv5j)|
-|125|[Valid Palindrome](./Algorithms/125.Valid-Palindrome)|26%|Easy||
+|125|[Valid Palindrome](./Algorithms/125.Valid-Palindrome)|27.0%|Easy||
 |126|[Word Ladder II](./Algorithms/126.word-ladder-ii)|14%|Hard|[❤](https://leetcode.com/list/oussv5j)|
 |127|[Word Ladder](./Algorithms/127.word-ladder)|20%|Medium|[❤](https://leetcode.com/list/oussv5j)|
 |128|[Longest Consecutive Sequence](./Algorithms/128.longest-consecutive-sequence)|38%|Hard||