<p>You are given an array of strings <code>words</code> and a string <code>chars</code>.</p>

<p>A string is <strong>good</strong> if it can be formed by characters from <code>chars</code> (each character can only be used once).</p>

<p>Return <em>the sum of lengths of all good strings in words</em>.</p>

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

<pre>
<strong>Input:</strong> words = [&quot;cat&quot;,&quot;bt&quot;,&quot;hat&quot;,&quot;tree&quot;], chars = &quot;atach&quot;
<strong>Output:</strong> 6
<strong>Explanation:</strong> The strings that can be formed are &quot;cat&quot; and &quot;hat&quot; so the answer is 3 + 3 = 6.
</pre>

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

<pre>
<strong>Input:</strong> words = [&quot;hello&quot;,&quot;world&quot;,&quot;leetcode&quot;], chars = &quot;welldonehoneyr&quot;
<strong>Output:</strong> 10
<strong>Explanation:</strong> The strings that can be formed are &quot;hello&quot; and &quot;world&quot; so the answer is 5 + 5 = 10.
</pre>

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

<ul>
	<li><code>1 &lt;= words.length &lt;= 1000</code></li>
	<li><code>1 &lt;= words[i].length, chars.length &lt;= 100</code></li>
	<li><code>words[i]</code> and <code>chars</code> consist of lowercase English letters.</li>
</ul>

// Time:  O(m * n), m is the length of chars, n is the number of words
// Space: O(1)

class Solution {
public:
    int countCharacters(vector<string>& words, string chars) {
        const auto& count = counter(chars);
        int result = 0;
        for (const auto& word : words) {
            if (check(word, chars, count)) {
                result += word.length();
            }
        }
        return result;
    }

private:
    unordered_map<char, int> counter(const string& s) {
        unordered_map<char, int> result;
        for (const auto& c : s) {
            ++result[c];
        }
        return result;
    }
    
    bool check(const string& word, const string& chars,
               const unordered_map<char, int>& count) {
        if (word.length() > chars.length()) {
            return false;
        }
        unordered_map<char, int> curr_count;
        for (const auto& c : word) {
            ++curr_count[c];
            if (!count.count(c) || count.at(c) < curr_count[c]) {
                return false;
            }
        }
        return true;
    }
};

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