Create 1857. Largest Color Value in a Directed Graph (#805)

Author: Chayandas07

1857. Largest Color Value in a Directed Graph

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+class Solution {
+public:
+    int maxi = -1;
+    int dp[100001][26];
+    bool dfs(int node, vector<int> adj[], vector<int>& vis, string& colors) {
+        vis[node] = 1;
+        dp[node][colors[node] - 'a']++;
+        for (auto it : adj[node]) {
+            if (!vis[it]) {
+                if (dfs(it, adj, vis, colors))
+                    return true;
+            }
+            
+            for (int i = 0; i < 26; i++) 
+                if (colors[node] - 'a' == i)
+                    dp[node][i] = max(dp[node][i], dp[it][i] + 1);
+                else
+                    dp[node][i] = max(dp[node][i], dp[it][i]);
+        }
+        for(int i=0;i<26;i++)maxi=max(maxi,dp[node][i]);
+        return false;
+    }
+    int largestPathValue(string colors, vector<vector<int>>& edges) {
+        int n = colors.size();
+        memset(dp, 0, sizeof(dp));
+        vector<int> adj[n];
+        queue<int> q, p;
+        vector<int> indegree(n, 0);
+        // creating adjacency matrix
+        for (auto it : edges) {
+            adj[it[0]].push_back(it[1]);
+            indegree[it[1]]++;
+        }
+        // topological sort using kahn's algo
+        for (int i = 0; i < n; i++)
+            if (indegree[i] == 0) {
+                q.push(i);
+                p.push(i);
+            }
+        vector<int> z;
+        while (!p.empty()) {
+            int node = p.front();
+            p.pop();
+            z.push_back(node);
+            for (auto it : adj[node]) {
+                indegree[it]--;
+                if (indegree[it] == 0)
+                    p.push(it);
+            }
+        }
+        //if cycle is present return -1
+        if (z.size() != n)
+            return -1;
+        vector<int> vis(n, false), pathvis(n, false);
+        // making dfs calls only for nodes  which have zero indegree
+        // other nodes will be included automatically in 
+        // the dp table by dfc calls of these nodes
+        while (!q.empty()) {
+            int node = q.front();
+            q.pop();
+            if (dfs(node, adj, vis, colors))
+                return -1;
+        }
+        return maxi;
+    }
+};