20.有效的括号.md

title	有效的括号
categories	leetcode leetcode题解

package main

/*
 * @lc app=leetcode.cn id=20 lang=golang
 *
 * [20] 有效的括号
 */

// @lc code=start
type (
	Stack struct {
		top    *node
		length int
	}
	node struct {
		value int
		prev  *node
	}
)

// Create a new stack
func New() *Stack {
	return &Stack{nil, 0}
}

// Return the number of items in the stack
func (this *Stack) Len() int {
	return this.length
}

// View the top item on the stack
func (this *Stack) Peek() int {
	if this.length == 0 {
		return 0
	}
	return this.top.value
}

// Pop the top item of the stack and return it
func (this *Stack) Pop() int {
	if this.length == 0 {
		return 0
	}

	n := this.top
	this.top = n.prev
	this.length--
	return n.value
}

// Push a value onto the top of the stack
func (this *Stack) Push(value int) {
	n := &node{value, this.top}
	this.top = n
	this.length++
}

// 123 {
// 91  [
// 40  (
// 41	)
// 93	]
// 125	}
//主函数
func isValid(s string) bool {
	bracket := New()

	for _, v := range s {
		switch v {
		case 123:
			bracket.Push(int(v))
		case 91:
			bracket.Push(int(v))
		case 40:
			bracket.Push(int(v))
		case 41:
			topValue := bracket.Pop()
			if (int(v) - topValue) != 1 {
				return false
			}
		case 93:
			topValue := bracket.Pop()
			if (int(v) - topValue) != 2 {
				return false
			}
		case 125:
			topValue := bracket.Pop()
			if (int(v) - topValue) != 2 {
				return false
			}

		}
	}
	if bracket.Len() != 0 {
		return false
	}

	return true
}

// @lc code=end