[LeetCode]Valid Parentheses

Q：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.

这道题是括号匹配问题，考察的是栈的基本使用。

我定义了一个括弧的优先级表，若当前字符优先级大于栈顶字符（1），则弹出栈顶字符；若当前字符优先级小于栈顶字符（0），则当前字符入栈。最后观察栈是否为空，若为空，则括弧配对，否则不配对。优先级表如下图：

下面贴上代码：

#include <iostream>#include<stack>using namespace std;class Solution {public:int replace(char c){if (c == '(')return 0;if (c == ')')return 1;if (c == '[')return 2;if (c == ']')return 3;if (c == '{')return 4;if (c == '}')return 5;}bool isValid(string s) {if (s.length() == 0 || s.length() == 1)return false;int ch[6][6] = { { 0, 1, 0, 0, 0, 0 },{ 0, 0, 0, 0, 0, 0 },{ 0, 0, 0, 1, 0, 0 },{ 0, 0, 0, 0, 0, 0 },{ 0, 0, 0, 0, 0, 1 },{ 0, 0, 0, 0, 0, 0 }};stack<char> ss;for (int i = 0; i < s.length(); i++){if (ss.empty()){ss.push(s[i]);continue;}char c = ss.top();if (ch[replace(c)][replace(s[i])])ss.pop();elsess.push(s[i]);}if (ss.empty())return true;elsereturn false;}};int main() {Solution s;cout << s.isValid("()[]{}()") << endl;cout << s.isValid("(([]{}))") << endl;cout << s.isValid("([]}") << endl;return 0;}