backtrace 21

2 files changed, 94 insertions, 1 deletions

diff --git a/src/2015/day21/aoc.cpp b/src/2015/day21/aoc.cpp
index 1c33c66..8c7e259 100644
--- a/src/2015/day21/aoc.cpp
+++ b/src/2015/day21/aoc.cpp
@@ -2,4 +2,22 @@
 
 namespace aoc2015 {
 
+int day21() {
+  Role me{100, 0, 0, 0};
+  Role boss{100, 8, 2, 0};
+  RPG game;
+
+  int money{INT32_MAX};
+  std::vector<Role> rs = game.shop(me);
+  std::for_each(rs.begin(), rs.end(), [&game, &boss, &money](Role& r) {
+    Role b = boss;
+    if (game.battle(r, b)) {
+      if (r.cost < money) {
+        money = r.cost;
+      }
+    }
+  });
+  return money;
 }
+
+} // namespace aoc2015
diff --git a/src/2015/day21/aoc.h b/src/2015/day21/aoc.h
index c439c03..126613e 100644
--- a/src/2015/day21/aoc.h
+++ b/src/2015/day21/aoc.h
@@ -1,6 +1,81 @@
 #pragma once
 #include "common.h"
+#include <algorithm>
+#include <vector>
 
 namespace aoc2015 {
 
-}
+struct Role {
+  int hitpoints;
+  int damage;
+  int armor;
+  int cost;
+};
+
+struct RPG {
+  struct item {
+    line_view name;
+    int cost;
+    int damage;
+    int armor;
+  };
+
+  // 1 in 5
+  item weapons[5] = {
+      {"dagger", 8, 4, 0},     {"shortsword", 10, 5, 0}, {"warhammer", 25, 6, 0},
+      {"longsword", 40, 7, 0}, {"greataxe", 74, 8, 0},
+  };
+
+  // 0, 1 in 5
+  item armors[5] = {
+      {"leather", 13, 0, 1},    {"chainmail", 31, 0, 2},  {"splintmail", 53, 0, 3},
+      {"bandedmail", 75, 0, 4}, {"platemail", 102, 0, 5},
+  };
+
+  // 0, 1, 2 in 6
+  item rings[6] = {
+      {"ring1", 25, 1, 0}, {"ring2", 50, 2, 0}, {"ring3", 100, 3, 0},
+      {"ring4", 20, 0, 1}, {"ring5", 40, 0, 2}, {"ring6", 80, 0, 3},
+  };
+
+  struct three {
+    int i1;
+    int i2;
+    int i3;
+  };
+
+  // backtrace
+  void shop(int i, three& t1, three& t2, std::vector<item>& is) {
+    if (i == 3) {
+
+    }
+  }
+
+  std::vector<Role> shop(Role r) {
+    std::vector<item> is;
+    std::vector<Role> rs;
+    three t1;
+    three t2;
+    shop(0, t1, t2, is);
+    std::transform(is.begin(), is.end(), rs.begin(), [&r](const item& i) -> Role {
+      Role x = r;
+      x.cost += i.cost;
+      x.armor += i.armor;
+      x.damage += i.damage;
+      return x;
+    });
+    return rs;
+  }
+
+  bool battle(Role& r1, Role& r2) {
+    while (r1.hitpoints > 0 && r2.hitpoints > 0) {
+      r2.hitpoints -= (r1.damage - r2.armor) > 0 ? r1.damage - r2.armor : 1;
+      r1.hitpoints -= (r2.damage - r1.armor) > 0 ? r2.damage - r1.armor : 1;
+    }
+    return r1.hitpoints > 0 || r2.hitpoints <= 0;
+  }
+};
+
+int day21();
+
+} // namespace aoc2015