1. Valid Parentheses（没有AC）

leetcode

Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid（有效的）.

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

bool isValid(char* s) {
        int len;
        len=strlen(s);
        if(len==0)
            return true;
        char str[len+1];
        int top=0;
        for(int i=0;i<len+1;i++){
            switch(s[i]){
                case '(':str[++top]='(';
                         break;
                case '[':str[++top]='[';
                         break;
                case '{':str[++top]='{';
                         break;
                case ')':if(str[top]=='(') --top;
                         if(top!=0) return false;
                         break;
                case ']':if(str[top]=='[') --top;
                         if(top!=0) return false;
                         break;
                case '}':if(str[top]=='{') --top;
                         if(top!=0) return false;
                         break;
            }
    }
    return true;
}