<p>Given two strings <code>s1</code> and <code>s2</code>, return <code>true</code><em> if </em><code>s2</code><em> contains a permutation of </em><code>s1</code><em>, or </em><code>false</code><em> otherwise</em>.</p>

<p>In other words, return <code>true</code> if one of <code>s1</code>&#39;s permutations is the substring of <code>s2</code>.</p>

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

<pre>
<strong>Input:</strong> s1 = &quot;ab&quot;, s2 = &quot;eidbaooo&quot;
<strong>Output:</strong> true
<strong>Explanation:</strong> s2 contains one permutation of s1 (&quot;ba&quot;).
</pre>

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

<pre>
<strong>Input:</strong> s1 = &quot;ab&quot;, s2 = &quot;eidboaoo&quot;
<strong>Output:</strong> false
</pre>

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

<ul>
	<li><code>1 &lt;= s1.length, s2.length &lt;= 10<sup>4</sup></code></li>
	<li><code>s1</code> and <code>s2</code> consist of lowercase English letters.</li>
</ul>

class Solution {
public:

    std::unordered_map<char, int> string2map(std::string::const_iterator begin,
                                             std::string::const_iterator end
                                            ) {
        std::unordered_map<char, int> mmap;
        for (std::string::const_iterator iter = begin; iter != end; ++iter) {
            const char& c = *iter;
            if (mmap.find(c) == mmap.end()) {
                mmap.insert(std::make_pair(c, 1));
            }
            else {
                ++mmap[c];
            }
        }
        return mmap;
    }

    bool checkInclusion(string s1, string s2) {

        if (s1.size() > s2.size()) return false;

        std::unordered_map<char, int> s1map = string2map(s1.begin(), s1.end());

        std::string::const_iterator l = s2.begin();
        std::string::const_iterator r = s2.begin();
        for (int i = 0; i < s1.size(); ++i) {
            ++r;
        }

        while (r != s2.end()+1) {
            std::unordered_map<char, int> windowMap = string2map(l, r);
            if (s1map == windowMap) return true;

            ++l;
            ++r;
        }

        return false;
    }
};
85315