airport_routes.cpp

puzzles/training/airport_routes.cpp

@@ -0,0 +1,178 @@
+/*
+VIM: let b:cf5build="clang -std=c++20 -O2 -pthread -lstdc++ -I. {SRC} -o {OUT}"
+VIM: let b:cf5run="{OUT}"
+VIM-: let b:cppflags=g:Iboost.g:Itbb
+VIM-: let b:ldflags=g:Lboost.g:Ltbb
+VIM-: let b:ldlibpath=g:Bboost.g:Btbb
+*/
+#include <iostream>
+#include <exception>
+#include <chrono>
+#include <string>
+#include <vector>
+#include <unordered_map>
+#include <unordered_set>
+#include <functional>
+
+/*
+Implement a class called AirMap that has two methods:
+
+1- add_route(start, destination)
+	- adds a ONE WAY connecting flight from start to destination
+
+2- print_all_routes(start, destination)
+	- prints all possible routes from start to destination irrespective of hops
+
+Sample inputs - Expected outputs
+Given the following flight routes, print all possible routes between the airports C and D
+
+  A ----> B
+  B ----> A
+  A ----> C
+  C ----> A
+  A ----> D
+  D ----> A
+  B ----> C
+  C ----> B
+  B ----> D
+  D ----> B
+Expected output:
+
+  C,A,B,D,
+  C,A,D,
+  C,B,A,D,
+  C,B,D,
+
+Input corner cases
+Find all routes from A to C
+
+No route example:
+
+A ----> B
+C ----> B
+C ----> A
+
+Expected output:
+
+"No route was found" message or an empty output
+Source equals destination example: Find all routes from A to A
+
+A ----> B
+B ----> C
+C ----> A
+Expected output:
+
+A
+*/
+
+class AirMap
+{
+    std::unordered_map<std::string, std::unordered_set<std::string>> graph_;
+
+public:
+    void add_route(const std::string& start, const std::string& destination)
+    {
+        graph_[start].insert(destination);
+    }
+
+    void print_all_routes(
+            const std::string& start,
+            const std::string& destination) const
+    {
+        std::unordered_set<std::string> visited;
+        std::vector<std::string> path;
+
+        print_all_routes_helper(start, destination, visited, path,
+            [](const std::vector<std::string>& path){
+                for (const auto& node : path){
+                    std::cout << node << ',';
+                }
+                std::cout << std::endl;
+            });
+    }
+
+    void print_all_routes_helper(
+            const std::string& start,
+            const std::string& destination,
+            std::unordered_set<std::string>& visited,
+            std::vector<std::string>& path,
+            std::function<void (const std::vector<std::string>& path)> fn) const
+    {
+        visited.insert(start);
+        path.push_back(start);
+
+        if (start == destination){
+            fn(path);
+        } else {
+            const auto it = graph_.find(start);
+            if ( it != graph_.end()){
+                for (const auto& node : it->second){
+                    if ( !visited.contains(node) ){
+                        print_all_routes_helper(node, destination, visited, path, fn);
+                    }
+                }
+            }
+        }
+
+        visited.erase(start);
+        path.pop_back();
+    }
+};
+
+int main ( void )
+{try{
+    auto begin = std::chrono::high_resolution_clock::now();
+
+
+    AirMap map;
+    map.add_route("A","B");
+    map.add_route("B","A");
+    map.add_route("B","D");
+    map.add_route("A","D");
+    map.add_route("A","C");
+    map.add_route("C","A");
+    map.add_route("C","B");
+    map.add_route("B","C");
+    map.add_route("D","A");
+    map.add_route("D","B");
+
+    map.print_all_routes("C", "D");
+    //......
+
+    {
+        std::cout << "---------------------------------------" << std::endl;
+        AirMap map;
+        map.add_route("A","B");
+        map.add_route("C","A");
+        map.add_route("C","B");
+        map.print_all_routes("A", "C");
+    }
+
+    {
+        std::cout << "---------------------------------------" << std::endl;
+        AirMap map;
+        map.add_route("A","B");
+        map.add_route("B","C");
+        map.add_route("C","A");
+        map.print_all_routes("A", "A");
+    }
+
+
+
+    auto end = std::chrono::high_resolution_clock::now();
+    std::chrono::duration<double> seconds = end - begin;
+    std::cout << "Time: " << seconds.count() << std::endl;
+    return 0;
+}
+catch ( const std::exception& e )
+{
+    std::cerr << std::endl
+            << "std::exception(\"" << e.what() << "\")." << std::endl;
+    return 2;
+}
+catch ( ... )
+{
+    std::cerr  << std::endl
+            << "unknown exception." << std::endl;
+    return 1;
+}}