Remove "all" files, add basic graph template

Author: adamant-pwn

cp-algo/all

@@ -0,0 +1,42 @@
+#ifndef CP_ALGO_GRAPH_BASE_HPP
+#define CP_ALGO_GRAPH_BASE_HPP
+#include <iostream>
+#include <ranges>
+#include <vector>
+namespace cp_algo::graph {
+    enum type {directed = 0, undirected = 1};
+    template<type undirected>
+    struct graph {
+        graph(size_t n, size_t v0 = 0): n(n), v0(v0), adj(n) {}
+
+        void add_edge(size_t u, size_t v) {
+            adj[u - v0].push_back(size(to));
+            to.push_back(v - v0);
+            if constexpr (undirected) {
+                adj[v - v0].push_back(size(to));
+            }
+            to.push_back(u - v0);
+        }
+        void read_edges(size_t m) {
+            for(size_t i = 0; i < m; i++) {
+                int u, v;
+                std::cin >> u >> v;
+                add_edge(u, v);
+            }
+        }
+        auto adjacent_generator(size_t v) const {
+            return [&adj = adj[v], idx = 0]() mutable {
+                return idx < ssize(adj) ? adj[idx++] : -1;
+            };
+        }
+        auto nodes_view() const {
+            return std::views::iota((size_t)0, n);
+        }
+
+        size_t n;
+        size_t v0;
+        std::vector<size_t> to;
+        std::vector<std::vector<size_t>> adj;
+    };
+}
+#endif // CP_ALGO_GRAPH_BASE_HPP

cp-algo/data_structures/all

@@ -0,0 +1,41 @@
+#ifndef CP_ALGO_GRAPH_CYCLE_HPP
+#define CP_ALGO_GRAPH_CYCLE_HPP
+#include "base.hpp"
+#include <algorithm>
+#include <vector>
+namespace cp_algo::graph {
+    std::vector<size_t> find_cycle(auto const& g) {
+        std::vector<char> state(g.n);
+        std::vector<size_t> cycle;
+        auto dfs = [&](auto self, size_t v, size_t pe) -> bool {
+            state[v] = 1;
+            auto gen = g.adjacent_generator(v);
+            for(size_t e = gen(); ~e; e = gen()) {
+                if(e / 2 != pe / 2) {
+                    auto u = g.to[e];
+                    if(state[u] == 0) {
+                        if(self(self, u, e)) {
+                            if(g.to[cycle[0]] != g.to[cycle.back() ^ 1]) {
+                                cycle.push_back(e);
+                            }
+                            return true;
+                        }
+                    } else if(state[u] == 1) {
+                        cycle = {e};
+                        return true;
+                    }
+                }
+            }
+            state[v] = 2;
+            return false;
+        };
+        for(size_t i: g.nodes_view()) {
+            if(!state[i] && dfs(dfs, i, -1)) {
+                break;
+            }
+        }
+        std::ranges::reverse(cycle);
+        return cycle;
+    }
+}
+#endif // CP_ALGO_GRAPH_CYCLE_HPP