Valid Parentheses
<p>Given a string <code>s</code> containing just the characters <code>&#39;(&#39;</code>, <code>&#39;)&#39;</code>, <code>&#39;{&#39;</code>, <code>&#39;}&#39;</code>, <code>&#39;[&#39;</code> and <code>&#39;]&#39;</code>, determine if the input string is valid.</p>

<p>An input string is valid if:</p>

<ol>
	<li>Open brackets must be closed by the same type of brackets.</li>
	<li>Open brackets must be closed in the correct order.</li>
	<li>Every close bracket has a corresponding open bracket of the same type.</li>
</ol>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;()&quot;</span></p>

<p><strong>Output:</strong> <span class="example-io">true</span></p>
</div>

<p><strong class="example">Example 2:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;()[]{}&quot;</span></p>

<p><strong>Output:</strong> <span class="example-io">true</span></p>
</div>

<p><strong class="example">Example 3:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;(]&quot;</span></p>

<p><strong>Output:</strong> <span class="example-io">false</span></p>
</div>

<p><strong class="example">Example 4:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;([])&quot;</span></p>

<p><strong>Output:</strong> <span class="example-io">true</span></p>
</div>

<p><strong class="example">Example 5:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">s = &quot;([)]&quot;</span></p>

<p><strong>Output:</strong> <span class="example-io">false</span></p>
</div>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 10<sup>4</sup></code></li>
	<li><code>s</code> consists of parentheses only <code>&#39;()[]{}&#39;</code>.</li>
</ul>
Stack; String
func isValid(s string) bool {
	stk := []rune{}
	for _, c := range s {
		if c == '(' || c == '{' || c == '[' {
			stk = append(stk, c)
		} else if len(stk) == 0 || !match(stk[len(stk)-1], c) {
			return false
		} else {
			stk = stk[:len(stk)-1]
		}
	}
	return len(stk) == 0
}

func match(l, r rune) bool {
	return (l == '(' && r == ')') || (l == '[' && r == ']') || (l == '{' && r == '}')
}