Initial commit

2015/puzzle-02-02.cc

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+#include <algorithm>
+#include <cassert>
+#include <iostream>
+#include <string>
+
+struct Box {
+  /** Construct box.
+   *  \param s String representation of dimensions 'lxwxh'
+   */
+  Box(std::string const &s) {
+    std::size_t pos = 0;
+    l_ = std::stoul(s, &pos, 10);
+    assert(s[pos] == 'x');
+    auto s2 = s.substr(pos + 1);
+    w_ = std::stoul(s2, &pos, 10);
+    assert(s2[pos] == 'x');
+    s2 = s2.substr(pos + 1);
+    h_ = std::stoul(s2, &pos, 10);
+    assert(pos == s2.length());
+  }
+
+  // How much paper does this box need?
+  unsigned long paper_needed() const {
+    unsigned long s1 = l_ * w_;
+    unsigned long s2 = w_ * h_;
+    unsigned long s3 = h_ * l_;
+    return 2 * (s1 + s2 + s3) + std::min({s1, s2, s3});
+  }
+
+  // How much ribbon do we need?
+  unsigned long ribbon_needed() const {
+    // The various side perimeters - we want the min of these multiplied by
+    // volume.
+    unsigned long p1 = 2 * (l_ + w_);
+    unsigned long p2 = 2 * (w_ + h_);
+    unsigned long p3 = 2 * (h_ + l_);
+    return l_ * w_ * h_ + std::min({p1, p2, p3});
+  }
+
+  unsigned long l_;
+  unsigned long w_;
+  unsigned long h_;
+};
+
+int main(int argc, char **argv) {
+  unsigned long total = 0;
+  for (std::string line; std::getline(std::cin, line);) {
+    Box b(line);
+    auto amount = b.ribbon_needed();
+    std::cout << "Box " << line << " needs " << amount << " feet of ribbon\n";
+    total += amount;
+  }
+  std::cout << "Total = " << total << " feet of ribbon\n";
+
+  return 0;
+}