Day 24 - Electromagnetic Moat

watmough · Dec 24, 2017 · 61ae879 · 61ae879
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diff --git a/.vscode/settings.json b/.vscode/settings.json
@@ -6,6 +6,7 @@
         "ios": "cpp",
         "iosfwd": "cpp",
         "type_traits": "cpp",
-        "xutility": "cpp"
+        "xutility": "cpp",
+        "utility": "cpp"
     }
 }
diff --git a/README.md b/README.md
@@ -1,6 +1,133 @@
 # Advent-of-Code-2017 
 
-### Day 22 - Coprocessor Conflagration
+### Day 24 - Electromagnetic Moat
+
+Rank: 2240 / 2221
+
+Search space algorithms beyond just a simple flood-fill or dumping a tree are
+somewhat of a blindspot I'm fixing in my coding.
+
+Part 1:
+What is the strength of the strongest bridge you can make with the components you have available?
+
+Part 2:
+What is the strength of the longest bridge you can make? If you can make multiple bridges of the 
+longest length, pick the strongest one.
+
+```C++
+// Advent of Code 2016
+// Day 24 - Electromagnetic Moat
+
+#include <iostream>
+#include <fstream>
+#include <sstream>
+#include <vector>
+#include <string>
+#include <tuple>
+#include <algorithm>
+using namespace std;
+
+// parse input
+void parse(vector<pair<int,int>>& parts)
+{
+    auto row{""s};
+    auto p1{0},p2{0};
+    ifstream data("day_24.inp");
+    while (getline(data,row)) {
+        stringstream line(row);
+        line >> p1; line.get();
+        line >> p2;
+        parts.push_back(pair<int,int>(p1,p2));
+    }
+}
+
+bool not_used(vector<int> used, int part_num)
+{
+    return find(begin(used),end(used),part_num)==end(used);
+}
+
+bool can_use(pair<int,int> part, int port)
+{
+    return part.first==port || part.second==port;
+}
+
+vector<int> get_moves(vector<pair<int,int>>& parts, vector<int> used,int port)    // components matching port that have not been used
+{
+    vector<int> moves;
+    for (int i=0;i<parts.size();++i) {
+        if (not_used(used,i) && can_use(parts[i],port)) {
+            moves.push_back(i);
+        }
+    }
+    return moves;
+}
+
+// Part 1 - Just solve for best strength
+tuple<int,vector<int>> solve_strength(vector<pair<int,int>>& parts, vector<int> used, int port, int strength)
+{
+    vector<int> moves = get_moves(parts,used,port);
+    auto best_strength = strength;
+    vector<int> best_path = used;
+    for (auto m : moves) {
+        used.push_back(m);
+        auto new_port = parts[m].first==port ? parts[m].second : parts[m].first;
+        auto new_strength = strength+parts[m].first+parts[m].second;
+        auto solution = solve_strength(parts,used,new_port,new_strength);
+        if (get<0>(solution)>best_strength) {
+            best_strength = get<0>(solution);
+            best_path = get<1>(solution);
+        }
+        used.pop_back();
+    }
+    return make_tuple(best_strength,best_path);
+}
+
+// Part 2 - Solve for longest path
+tuple<int,int,vector<int>> solve_length(vector<pair<int,int>>& parts, vector<int> used, int port, int strength,int length)
+{
+    vector<int> moves = get_moves(parts,used,port);
+    auto best_length = length;
+    auto best_strength = strength;
+    vector<int> best_path = used;
+    for (auto m : moves) {
+        used.push_back(m);
+        auto new_port = parts[m].first==port ? parts[m].second : parts[m].first;
+        auto new_strength = strength+parts[m].first+parts[m].second;
+        auto new_length = length+1;
+        auto solution = solve_length(parts,used,new_port,new_strength,new_length);
+        if (get<0>(solution)>best_length || (get<0>(solution)==best_length && get<1>(solution)>best_strength)) {
+            best_length = get<0>(solution);
+            best_strength = get<1>(solution);
+            best_path = get<2>(solution);
+        }
+        used.pop_back();
+    }
+    return make_tuple(best_length,best_strength,best_path);
+}
+
+int main()
+{
+    vector<pair<int,int>> parts;
+    parse(parts);
+
+    auto solution_strength = solve_strength(parts,vector<int>{},0,0);
+    cout << "Part 1: " << get<0>(solution_strength) << endl;
+
+    auto solution_length = solve_length(parts,vector<int>{},0,0,0);
+    cout << "Part 2: " << get<1>(solution_length) << endl;
+
+    return 0;
+}
+```
+
+Output:
+
+```
+Part 1: 1906
+Part 2: 1824
+```
+
+### Day 23 - Coprocessor Conflagration
 
 Rank: 345 / ---
 

diff --git a/day_24.cpp b/day_24.cpp
@@ -0,0 +1,110 @@
+// Advent of Code 2016
+// Day 24 - Electromagnetic Moat
+
+#include <iostream>
+#include <fstream>
+#include <sstream>
+#include <vector>
+#include <string>
+#include <tuple>
+#include <algorithm>
+using namespace std;
+
+// parse input
+void parse(vector<pair<int,int>>& parts)
+{
+    auto row{""s};
+    auto p1{0},p2{0};
+    ifstream data("day_24.inp");
+    while (getline(data,row)) {
+        stringstream line(row);
+        line >> p1; line.get();
+        line >> p2;
+        parts.push_back(pair<int,int>(p1,p2));
+    }
+}
+
+bool not_used(vector<int> used, int part_num)
+{
+    return find(begin(used),end(used),part_num)==end(used);
+}
+
+bool can_use(pair<int,int> part, int port)
+{
+    return part.first==port || part.second==port;
+}
+
+vector<int> get_moves(vector<pair<int,int>>& parts, vector<int> used,int port)    // components matching port that have not been used
+{
+    vector<int> moves;
+    for (int i=0;i<parts.size();++i) {
+        if (not_used(used,i) && can_use(parts[i],port)) {
+            moves.push_back(i);
+        }
+    }
+    return moves;
+}
+
+// Part 1 - Just solve for best strength
+tuple<int,vector<int>> solve_strength(vector<pair<int,int>>& parts, vector<int> used, int port, int strength)
+{
+    vector<int> moves = get_moves(parts,used,port);
+    auto best_strength = strength;
+    vector<int> best_path = used;
+    for (auto m : moves) {
+        used.push_back(m);
+        auto new_port = parts[m].first==port ? parts[m].second : parts[m].first;
+        auto new_strength = strength+parts[m].first+parts[m].second;
+        auto solution = solve_strength(parts,used,new_port,new_strength);
+        if (get<0>(solution)>best_strength) {
+            best_strength = get<0>(solution);
+            best_path = get<1>(solution);
+        }
+        used.pop_back();
+    }
+    return make_tuple(best_strength,best_path);
+}
+
+// Part 2 - Solve for longest path
+tuple<int,int,vector<int>> solve_length(vector<pair<int,int>>& parts, vector<int> used, int port, int strength,int length)
+{
+    vector<int> moves = get_moves(parts,used,port);
+    auto best_length = length;
+    auto best_strength = strength;
+    vector<int> best_path = used;
+    for (auto m : moves) {
+        used.push_back(m);
+        auto new_port = parts[m].first==port ? parts[m].second : parts[m].first;
+        auto new_strength = strength+parts[m].first+parts[m].second;
+        auto new_length = length+1;
+        auto solution = solve_length(parts,used,new_port,new_strength,new_length);
+        if (get<0>(solution)>best_length || (get<0>(solution)==best_length && get<1>(solution)>best_strength)) {
+            best_length = get<0>(solution);
+            best_strength = get<1>(solution);
+            best_path = get<2>(solution);
+        }
+        used.pop_back();
+    }
+    return make_tuple(best_length,best_strength,best_path);
+}
+
+int main()
+{
+    vector<pair<int,int>> parts;
+    parse(parts);
+
+    auto solution_strength = solve_strength(parts,vector<int>{},0,0);
+    cout << "Part 1: " << get<0>(solution_strength) << endl;
+
+    auto solution_length = solve_length(parts,vector<int>{},0,0,0);
+    cout << "Part 2: " << get<1>(solution_length) << endl;
+
+    return 0;
+}
+
+/*
+Output:
+
+Part 1: 1906
+Part 2: 1824
+*/
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