Added C++ solution for 3400-3499/3435. Frequencies of Shortest Supersequences

Author: ZAID646

solution/3400-3499/3435.Frequencies of Shortest Supersequences/Solutions.cpp

@@ -0,0 +1,248 @@
+#include <vector>
+#include <string>
+#include <queue>
+#include <stack>
+#include <set>
+#include <functional>
+using namespace std;
+
+class Solution
+{
+public:
+    vector<vector<int>> supersequences(vector<string> &words)
+    {
+        const int ALPHA = 26;
+        bool used[ALPHA] = {};
+        for (auto &w : words)
+            for (char c : w)
+                used[c - 'a'] = true;
+
+        vector<int> charMap(ALPHA, -1);
+        vector<char> chars;
+        int charCount = 0;
+        for (int c = 0; c < ALPHA; c++)
+        {
+            if (used[c])
+            {
+                charMap[c] = charCount++;
+                chars.push_back('a' + c);
+            }
+        }
+
+        vector<vector<bool>> graph(charCount, vector<bool>(charCount));
+        vector<bool> selfLoop(charCount);
+        for (auto &w : words)
+        {
+            int u = charMap[w[0] - 'a'], v = charMap[w[1] - 'a'];
+            if (u == v)
+                selfLoop[u] = true;
+            else
+                graph[u][v] = true;
+        }
+
+        vector<int> disc(charCount, -1), low(charCount), comp(charCount, -1);
+        vector<bool> inStack(charCount);
+        stack<int> stk;
+        int time = 0, sccTotal = 0;
+
+        function<void(int)> tarjan = [&](int u)
+        {
+            disc[u] = low[u] = time++;
+            stk.push(u);
+            inStack[u] = true;
+
+            for (int v = 0; v < charCount; v++)
+            {
+                if (!graph[u][v])
+                    continue;
+                if (disc[v] == -1)
+                {
+                    tarjan(v);
+                    low[u] = min(low[u], low[v]);
+                }
+                else if (inStack[v])
+                {
+                    low[u] = min(low[u], disc[v]);
+                }
+            }
+
+            if (low[u] == disc[u])
+            {
+                while (true)
+                {
+                    int v = stk.top();
+                    stk.pop();
+                    inStack[v] = false;
+                    comp[v] = sccTotal;
+                    if (v == u)
+                        break;
+                }
+                sccTotal++;
+            }
+        };
+
+        for (int i = 0; i < charCount; i++)
+            if (disc[i] == -1)
+                tarjan(i);
+
+        vector<vector<int>> sccGroups(sccTotal);
+        for (int i = 0; i < charCount; i++)
+            sccGroups[comp[i]].push_back(i);
+
+        vector<vector<int>> sccGraph(sccTotal);
+        vector<int> inDegree(sccTotal);
+        for (int u = 0; u < charCount; u++)
+        {
+            for (int v = 0; v < charCount; v++)
+            {
+                if (graph[u][v] && comp[u] != comp[v])
+                {
+                    sccGraph[comp[u]].push_back(comp[v]);
+                    inDegree[comp[v]]++;
+                }
+            }
+        }
+
+        queue<int> q;
+        vector<int> topoOrder;
+        for (int i = 0; i < sccTotal; i++)
+            if (inDegree[i] == 0)
+                q.push(i);
+
+        while (!q.empty())
+        {
+            int u = q.front();
+            q.pop();
+            topoOrder.push_back(u);
+            for (int v : sccGraph[u])
+            {
+                if (--inDegree[v] == 0)
+                    q.push(v);
+            }
+        }
+
+        auto isAcyclic = [](const vector<vector<bool>> &g, int mask, int n)
+        {
+            vector<bool> removed(n);
+            for (int i = 0; i < n; i++)
+                if (mask & (1 << i))
+                    removed[i] = true;
+
+            vector<int> deg(n);
+            for (int u = 0; u < n; u++)
+            {
+                if (removed[u])
+                    continue;
+                for (int v = 0; v < n; v++)
+                {
+                    if (!removed[v] && g[u][v])
+                        deg[v]++;
+                }
+            }
+
+            queue<int> q;
+            int cnt = 0;
+            int total = n - __builtin_popcount(mask);
+            for (int i = 0; i < n; i++)
+                if (!removed[i] && deg[i] == 0)
+                    q.push(i);
+
+            while (!q.empty())
+            {
+                int u = q.front();
+                q.pop();
+                cnt++;
+                for (int v = 0; v < n; v++)
+                {
+                    if (!removed[v] && g[u][v] && --deg[v] == 0)
+                        q.push(v);
+                }
+            }
+            return cnt == total;
+        };
+
+        auto findMinFVS = [&](const vector<vector<bool>> &g, int n)
+        {
+            set<vector<int>> patterns;
+            for (int sz = 0; sz <= n; sz++)
+            {
+                bool found = false;
+                for (int mask = 0; mask < (1 << n); mask++)
+                {
+                    if (__builtin_popcount(mask) != sz)
+                        continue;
+                    if (isAcyclic(g, mask, n))
+                    {
+                        vector<int> freq(n, 1);
+                        for (int i = 0; i < n; i++)
+                            if (mask & (1 << i))
+                                freq[i] = 2;
+                        patterns.insert(freq);
+                        found = true;
+                    }
+                }
+                if (found)
+                    break;
+            }
+            return vector<vector<int>>(patterns.begin(), patterns.end());
+        };
+
+        vector<vector<vector<int>>> sccPatterns(sccTotal);
+        for (int i = 0; i < sccTotal; i++)
+        {
+            auto &group = sccGroups[i];
+            if (group.size() == 1)
+            {
+                sccPatterns[i] = selfLoop[group[0]] ? vector<vector<int>>{{2}} : vector<vector<int>>{{1}};
+                continue;
+            }
+
+            vector<vector<bool>> subgraph(group.size(), vector<bool>(group.size()));
+            vector<int> localToGlobal(group.size());
+            for (int j = 0; j < group.size(); j++)
+            {
+                localToGlobal[j] = group[j];
+                if (selfLoop[group[j]])
+                    subgraph[j][j] = true;
+                for (int k = 0; k < group.size(); k++)
+                {
+                    if (graph[group[j]][group[k]])
+                        subgraph[j][k] = true;
+                }
+            }
+            sccPatterns[i] = findMinFVS(subgraph, group.size());
+        }
+
+        vector<vector<int>> result = {{}};
+        for (int scc : topoOrder)
+        {
+            vector<vector<int>> newResult;
+            for (auto &freq : result)
+            {
+                for (auto &pattern : sccPatterns[scc])
+                {
+                    vector<int> newFreq = freq;
+                    newFreq.resize(charCount);
+                    for (int i = 0; i < sccGroups[scc].size(); i++)
+                    {
+                        int globalIdx = sccGroups[scc][i];
+                        newFreq[globalIdx] = pattern[i];
+                    }
+                    newResult.push_back(newFreq);
+                }
+            }
+            result = move(newResult);
+        }
+
+        set<vector<int>> uniqueFreqs;
+        for (auto &freq : result)
+        {
+            vector<int> finalFreq(ALPHA);
+            for (int i = 0; i < charCount; i++)
+                finalFreq[chars[i] - 'a'] = freq[i];
+            uniqueFreqs.insert(finalFreq);
+        }
+
+        return vector<vector<int>>(uniqueFreqs.begin(), uniqueFreqs.end());
+    }
+};