<p>Given two strings <code>s</code> and <code>p</code>, return <em>an array of all the start indices of </em><code>p</code><em>&#39;s anagrams in </em><code>s</code>. You may return the answer in <strong>any order</strong>.</p>

<p>An <strong>Anagram</strong> is a word or phrase formed by rearranging the letters of a different word or phrase, typically using all the original letters exactly once.</p>

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

<pre>
<strong>Input:</strong> s = &quot;cbaebabacd&quot;, p = &quot;abc&quot;
<strong>Output:</strong> [0,6]
<strong>Explanation:</strong>
The substring with start index = 0 is &quot;cba&quot;, which is an anagram of &quot;abc&quot;.
The substring with start index = 6 is &quot;bac&quot;, which is an anagram of &quot;abc&quot;.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;abab&quot;, p = &quot;ab&quot;
<strong>Output:</strong> [0,1,2]
<strong>Explanation:</strong>
The substring with start index = 0 is &quot;ab&quot;, which is an anagram of &quot;ab&quot;.
The substring with start index = 1 is &quot;ba&quot;, which is an anagram of &quot;ab&quot;.
The substring with start index = 2 is &quot;ab&quot;, which is an anagram of &quot;ab&quot;.
</pre>

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

<ul>
	<li><code>1 &lt;= s.length, p.length &lt;= 3 * 10<sup>4</sup></code></li>
	<li><code>s</code> and <code>p</code> consist of lowercase English letters.</li>
</ul>

class Solution {
public:
    int findSum(vector<vector<int>> &prefix, int ind, int left, int right) {

        int r = prefix[ind][right];
        int l = 0;

        if (left > 0) {
            l = prefix[ind][left - 1];
        }

        return r - l;
    }   
    bool check(vector<vector<int>> &prefix, vector<int> &count, int left, int right) {
        
        for (auto ch = 'a'; ch <= 'z'; ch++) {
            int ind = ch - 'a';
            int expected = count[ind];
            int actual = findSum(prefix, ind, left, right);

            if (actual != expected) {
                return false;
            }
        }

        return true;
    }
    vector<int> findAnagrams(string str, string p) {
        int len = str.size();

        vector<vector<int>> prefix(26, vector<int> (len, 0));

        for (int i = 0; i < len; i++) {
            int ind = int(str[i] - 'a');

            prefix[ind][i] = 1;
        }

        for (int i = 0; i < 26; i++) {
            for (int j = 1; j < len; j++) {
                prefix[i][j] += prefix[i][j - 1];
            }
        }

        vector<int> count(26, 0);

        for (auto ch : p) {
            int ind = int(ch - 'a');
            count[ind] += 1;
        }

        int ps = p.size();

        vector<int> ans;

        for (int i = 0; i + ps <= len; i++) {
            int left = i, right = i + ps - 1;

            if (check(prefix, count, left, right)) {
                ans.push_back(i);
            }
        }

        return ans;
    }
};
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