DI String Match
<p>A permutation <code>perm</code> of <code>n + 1</code> integers of all the integers in the range <code>[0, n]</code> can be represented as a string <code>s</code> of length <code>n</code> where:</p>

<ul>
	<li><code>s[i] == &#39;I&#39;</code> if <code>perm[i] &lt; perm[i + 1]</code>, and</li>
	<li><code>s[i] == &#39;D&#39;</code> if <code>perm[i] &gt; perm[i + 1]</code>.</li>
</ul>

<p>Given a string <code>s</code>, reconstruct the permutation <code>perm</code> and return it. If there are multiple valid permutations perm, return <strong>any of them</strong>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> s = "IDID"
<strong>Output:</strong> [0,4,1,3,2]
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> s = "III"
<strong>Output:</strong> [0,1,2,3]
</pre><p><strong class="example">Example 3:</strong></p>
<pre><strong>Input:</strong> s = "DDI"
<strong>Output:</strong> [3,2,0,1]
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 10<sup>5</sup></code></li>
	<li><code>s[i]</code> is either <code>&#39;I&#39;</code> or <code>&#39;D&#39;</code>.</li>
</ul>
Greedy; Array; Two Pointers; String
impl Solution {
    pub fn di_string_match(s: String) -> Vec<i32> {
        let mut low = 0;
        let mut high = s.len() as i32;
        let mut ans = Vec::with_capacity(s.len() + 1);

        for c in s.chars() {
            if c == 'I' {
                ans.push(low);
                low += 1;
            } else {
                ans.push(high);
                high -= 1;
            }
        }

        ans.push(low);
        ans
    }
}
