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

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/valid-parentheses
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。

解答思路

可使用栈的特点进行解答。

代码

// 使用栈的思路进行解答
func isValid(s string) bool {
   var stack []string // 自定义栈
   for _, str := range s {
      switch str {
      case '(':
         fallthrough
      case '{':
         fallthrough
      case '[':
         // 入栈
         stack = append(stack, string(str))
         break
      case ')':
         // 查看是否相等并出栈
         if len(stack) == 0 {
            return false
         }
         ch := stack[len(stack)-1]
         if ch == "(" {
            // 出栈
            if len(stack) > 1 {
               stack = stack[0 : len(stack)-1]
            } else {
               stack = stack[0:0]
            }
            break
         }
         return false
      case '}':
         // 查看是否相等并出栈
         if len(stack) == 0 {
            return false
         }
         ch := stack[len(stack)-1]
         if ch == "{" {
            // 出栈
            if len(stack) > 1 {
               stack = stack[0 : len(stack)-1]
            } else {
               stack = stack[0:0]
            }
            break
         }
         return false
      case ']':
         // 查看是否相等并出栈
         if len(stack) == 0 {
            return false
         }
         ch := stack[len(stack)-1]
         if ch == "[" {
            // 出栈
            if len(stack) > 1 {
               stack = stack[0 : len(stack)-1]
            } else {
               stack = stack[0:0]
            }
            break
         }
         return false
      }
   }
   return len(stack) == 0
}

func TestIsValid(t *testing.T) {
   println(isValid("[{{}}]"))
}