leetcode_20_Valid Parentheses (easy)

Valid Parentheses

题目：

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

The brackets must close in the correct order, "()" and "()[]{}" are all valid but "(]" and "([)]" are not.

解题：
一看题目，就想到应该用栈的思想来做

#include <iostream>
using namespace std;

class Solution {
public:
    bool isValid(string s) {
        char a[100];
        for(int i=0;i<100;i++){
            a[i] = '0';
        }
        int end=0;
        for(int i = 0;i<s.size();i++){
            if(a[end]=='('){
                if(s.at(i)==')'){
                    a[end] = '0';
                    if(end>0)
                     end--;
                }else if(s.at(i)=='('||s.at(i)=='['||s.at(i)=='{'){
                    a[++end]=s.at(i);
                }else{
                    return false;
                }
            }else if(a[end]=='['){
                if(s.at(i)==']'){
                    a[end] = '0';
                    if(end>0)
                     end--;
                }else if(s.at(i)=='('||s.at(i)=='['||s.at(i)=='{'){
                    a[++end]=s.at(i);
                }else{
                    return false;
                }
            }else if(a[end]=='{'){
                if(s.at(i)=='}'){
                    a[end] = '0';
                    if(end>0)
                      end--;
                }else if(s.at(i)=='('||s.at(i)=='['||s.at(i)=='{'){
                    a[++end]=s.at(i);
                }else{
                    return false;
                }
            }else{
                if(s.at(i)=='('||s.at(i)=='['||s.at(i)=='{'){
                   a[end] = s.at(i);
                }else{
                    return false;
                }
            }

        }
        if(a[end]!='0'){
            return false;
        }
        return true;
    }
};

int main(int argc, const char * argv[]) {
    Solution a;
    cout<<a.isValid("{{})")<<endl;
    return 0;
}