<p>There is a <strong>directed graph</strong> of <code>n</code> colored nodes and <code>m</code> edges. The nodes are numbered from <code>0</code> to <code>n - 1</code>.</p>

<p>You are given a string <code>colors</code> where <code>colors[i]</code> is a lowercase English letter representing the <strong>color</strong> of the <code>i<sup>th</sup></code> node in this graph (<strong>0-indexed</strong>). You are also given a 2D array <code>edges</code> where <code>edges[j] = [a<sub>j</sub>, b<sub>j</sub>]</code> indicates that there is a <strong>directed edge</strong> from node <code>a<sub>j</sub></code> to node <code>b<sub>j</sub></code>.</p>

<p>A valid <strong>path</strong> in the graph is a sequence of nodes <code>x<sub>1</sub> -&gt; x<sub>2</sub> -&gt; x<sub>3</sub> -&gt; ... -&gt; x<sub>k</sub></code> such that there is a directed edge from <code>x<sub>i</sub></code> to <code>x<sub>i+1</sub></code> for every <code>1 &lt;= i &lt; k</code>. The <strong>color value</strong> of the path is the number of nodes that are colored the <strong>most frequently</strong> occurring color along that path.</p>

<p>Return <em>the <strong>largest color value</strong> of any valid path in the given graph, or </em><code>-1</code><em> if the graph contains a cycle</em>.</p>

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

<p><img alt="" src="https://assets.leetcode.com/uploads/2021/04/21/leet1.png" style="width: 400px; height: 182px;" /></p>

<pre>
<strong>Input:</strong> colors = &quot;abaca&quot;, edges = [[0,1],[0,2],[2,3],[3,4]]
<strong>Output:</strong> 3
<strong>Explanation:</strong> The path 0 -&gt; 2 -&gt; 3 -&gt; 4 contains 3 nodes that are colored <code>&quot;a&quot; (red in the above image)</code>.
</pre>

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

<p><img alt="" src="https://assets.leetcode.com/uploads/2021/04/21/leet2.png" style="width: 85px; height: 85px;" /></p>

<pre>
<strong>Input:</strong> colors = &quot;a&quot;, edges = [[0,0]]
<strong>Output:</strong> -1
<strong>Explanation:</strong> There is a cycle from 0 to 0.
</pre>

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

<ul>
	<li><code>n == colors.length</code></li>
	<li><code>m == edges.length</code></li>
	<li><code>1 &lt;= n &lt;= 10<sup>5</sup></code></li>
	<li><code>0 &lt;= m &lt;= 10<sup>5</sup></code></li>
	<li><code>colors</code> consists of lowercase English letters.</li>
	<li><code>0 &lt;= a<sub>j</sub>, b<sub>j</sub>&nbsp;&lt; n</code></li>
</ul>
class Solution {
public:
    vector<int> g[100005];
    int n, xl[100005], indeg[100005], f[100005], q[100005];
    string C;
    
    bool topo(){
        int head = 0, tail = 0, i, j;
        for (i = 0; i < n; ++i)
            if (indeg[i] == 0) xl[++tail] = i;
        while (head < tail){
            i = xl[++head];
            for (j = 0; j < g[i].size(); ++j)
                if (--indeg[g[i][j]] == 0) xl[++tail] = g[i][j];
        }

        return tail == n;
    }
    
    int largestPathValue(string CC, vector<vector<int>>& edges) {
        int i, j, c, res = 0;
        C = CC;
        n = CC.size();
        for (i = 0; i < n; ++i) g[i].clear();
        for (i = 0; i < n; ++i) indeg[i] = 0;
        for (auto e : edges){
            g[e[0]].push_back(e[1]);
            ++indeg[e[1]];
        }
        
        if (!topo()) return -1;
        for (c = 0; c < 26; ++c){
            for (i = 0; i < n; ++i){
                if (C[i] - 'a' == c) q[i] = 1;
                else q[i] = 0;
                f[i] = q[i];
            }
            
            for (int w = 1; w <= n; ++w){
                i = xl[w];
                res = max(res, f[i]);
                for (auto j : g[i]) f[j] = max(f[j], f[i] + q[j]);
            }
        }
        
        return res;
    }
};
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