valid parens

validparens/readme.md

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+20. Valid Parentheses
+Easy
+
+Given a string s 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.
+    Every close bracket has a corresponding open bracket of the same type.
+
+ 
+
+Example 1:
+
+Input: s = "()"
+Output: true
+
+Example 2:
+
+Input: s = "()[]{}"
+Output: true
+
+Example 3:
+
+Input: s = "(]"
+Output: false
+
+ 
+
+Constraints:
+
+    1 <= s.length <= 104
+    s consists of parentheses only '()[]{}'.
+
+

validparens/validparens.go

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+package validparens
+
+type stack struct {
+	store []rune
+}
+
+func (s *stack) Push(r rune) {
+	s.store = append(s.store, r)
+}
+
+func (s *stack) Pop() rune {
+	res := s.store[len(s.store)-1]
+	s.store = s.store[:len(s.store)-1]
+	return res
+}
+
+func (s *stack) Length() int {
+	return len(s.store)
+}
+
+func (s *stack) OnTop(r rune) bool {
+	if s.Length() == 0 {
+		return false
+	}
+	return s.store[len(s.store)-1] == r
+}
+
+func NewStack() stack {
+	store := make([]rune, 0)
+	return stack{
+		store: store,
+	}
+}
+
+func isValid(s string) bool {
+	history := NewStack()
+
+	for _, r := range s {
+		switch r {
+		case '{', '[', '(':
+			history.Push(r)
+		case ')':
+			if !history.OnTop('(') {
+				return false
+			}
+			history.Pop()
+		case ']':
+			if !history.OnTop('[') {
+				return false
+			}
+			history.Pop()
+		case '}':
+			if !history.OnTop('{') {
+				return false
+			}
+			history.Pop()
+		}
+
+	}
+
+	return history.Length() == 0
+}
+
+func IsValid(s string) bool {
+	return isValid(s)
+}

validparens/validparens_test.go

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+package validparens_test
+
+import (
+	"testing"
+
+	"git.jxs.me/leetgo/validparens"
+	"github.com/stretchr/testify/require"
+)
+
+func TestExamples(t *testing.T) {
+	cases := map[string]bool{
+		"":       true,
+		"(":      false,
+		"()":     true,
+		"[{()}]": true,
+		"[(])":   false,
+	}
+
+	for input, expected := range cases {
+		require.Equal(t, expected, validparens.IsValid(input))
+	}
+}