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20.valid-parentheses.cpp
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20.valid-parentheses.cpp
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/*
* @lc app=leetcode id=20 lang=cpp
*
* [20] Valid Parentheses
*/
#include <vector>
using namespace std;
// @lc code=start
class Solution
{
public:
typedef struct symbol
{
char c;
int cnt;
} symbol;
bool isValid(string s)
{
vector<symbol *> symbols = vector<symbol *>();
for (auto c : s)
{
switch (c)
{
case '(':
case '[':
case '{':
{
if (!symbols.empty())
{
symbol *top = symbols.back();
if (c == top->c)
{
top->cnt++;
}
else
{
symbols.push_back(new symbol{c, 1});
}
}
else
{
symbols.push_back(new symbol{c, 1});
}
break;
}
case ')':
case ']':
case '}':
{
if (symbols.empty())
{
return false;
}
symbol *top = symbols.back();
if (!is_match(top->c, c))
{
return false;
}
top->cnt--;
if (top->cnt == 0)
{
symbols.pop_back();
}
break;
}
default:
continue;
}
}
return symbols.empty();
}
bool is_match(char l, char r)
{
return (l == '(' && r == ')') || (l == '{' && r == '}') || (l == '[' && r == ']');
}
};
// @lc code=end