From 26cd07b4d31e09b8b5bacb1c4d1664d93313ca2e Mon Sep 17 00:00:00 2001
From: Santo Cariotti <santo@dcariotti.me>
Date: Wed, 18 Jan 2023 23:26:18 +0100
Subject: add dijkstra

---
 Year_2/Algorithms/dijkstra.cc | 175 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 175 insertions(+)
 create mode 100644 Year_2/Algorithms/dijkstra.cc

diff --git a/Year_2/Algorithms/dijkstra.cc b/Year_2/Algorithms/dijkstra.cc
new file mode 100644
index 0000000..9392e20
--- /dev/null
+++ b/Year_2/Algorithms/dijkstra.cc
@@ -0,0 +1,175 @@
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <queue>
+#include <vector>
+#define INF 999999
+
+using namespace std;
+
+template <class K, class H>
+class Graph {
+public:
+    Graph()
+    {
+    }
+
+    ~Graph()
+    {
+    }
+
+    Graph<K, H>*
+    add_node(K x)
+    {
+        auto it = nodes_.find(x);
+
+        if (it == nodes_.end()) {
+            nodes_.insert({ x, vector<pair<K, H>>() });
+            size_++;
+        }
+
+        return this;
+    }
+
+    Graph<K, H>*
+    add_edge(K x, K y, H w)
+    {
+        auto u = nodes_.find(x);
+        auto v = nodes_.find(y);
+
+        if (u != nodes_.end() && v != nodes_.end()) {
+            nodes_[x].push_back({ y, w });
+        }
+
+        return this;
+    }
+
+    size_t
+    dijkstra(K s, K r)
+    {
+        typedef pair<H, K> phk;
+        priority_queue<phk, vector<phk>, greater<phk>> pq;
+
+        auto i = nodes_.find(s);
+        auto j = nodes_.find(r);
+
+        if (i == nodes_.end() || j == nodes_.end()) {
+            return INF;
+        }
+
+        map<K, int> dist;
+
+        pq.push({ 0, s });
+
+        for (const auto& it : nodes_)
+            dist.insert({ it.first, INF });
+
+        dist[s] = 0;
+
+        while (!pq.empty()) {
+            int u = pq.top().second;
+            pq.pop();
+
+            for (auto const& i : nodes_[u]) {
+                int v = i.first;
+                int w = i.second;
+
+                if (dist[v] > dist[u] + w) {
+                    dist[v] = dist[u] + w;
+                    pq.push({ dist[v], v });
+                }
+            }
+        }
+
+        return dist[r];
+    }
+
+private:
+    size_t size_ { 0 };
+    map<K, vector<pair<K, H>>> nodes_;
+};
+
+int
+main(int argc, char** argv)
+{
+    int tasks = (argc > 1) ? stoi(argv[1]) : 100;
+    int n, m;
+    string buf;
+
+    ifstream fin("input.txt");
+    ofstream fout("output.txt");
+
+    for (int i = 0; i < tasks; ++i) {
+        string t;
+
+        fin >> n >> m >> t;
+
+        Graph<int, int>* g = new Graph<int, int>();
+        if (t == "int") {
+            int k;
+
+            for (int j = 0; j < n; ++j) {
+                fin >> k;
+                g->add_node(k);
+            }
+
+            int n1, n2, w;
+
+            for (int j = 0; j < m; ++j) {
+                fin >> buf;
+                n1 = stoi(buf.substr(1, buf.length()));
+                fin >> buf;
+                n2 = stoi(buf);
+                fin >> buf;
+                w = stoi(buf.substr(0, buf.length() - 1));
+
+                g->add_edge(n1, n2, w);
+            }
+            int s, r;
+            fin >> s >> r;
+
+            auto dist = g->dijkstra(s, r);
+            if (dist == INF)
+                fout << "inf." << endl;
+            else
+                fout << dist << endl;
+
+        } else {
+            double k;
+
+            for (int j = 0; j < n; ++j) {
+                fin >> k;
+                g->add_node(k * 10);
+            }
+
+            double n1, n2;
+            int w;
+
+            for (int j = 0; j < m; ++j) {
+                fin >> buf;
+                n1 = stod(buf.substr(1, buf.length()));
+                fin >> buf;
+                n2 = stod(buf);
+                fin >> buf;
+                w = stoi(buf.substr(0, buf.length() - 1));
+
+                g->add_edge(n1 * 10, n2 * 10, w);
+            }
+
+            double s, r;
+            fin >> s >> r;
+
+            auto dist = g->dijkstra(s * 10, r * 10);
+            if (dist == INF)
+                fout << "inf." << endl;
+            else
+                fout << dist << endl;
+        }
+        delete g;
+    }
+
+    fin.close();
+    fout.close();
+
+    return 0;
+}
-- 
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