Initial commit

2020/puzzle-09-02.cc

@@ -0,0 +1,77 @@
+#include <algorithm>
+#include <cassert>
+#include <iostream>
+#include <list>
+#include <map>
+#include <regex>
+#include <string>
+
+template <std::size_t L> struct Buffer {
+  Buffer() {}
+
+  bool add_value(std::string const &s) {
+    unsigned long i = std::stoul(s);
+    bool result = true;
+    auto size = buf_.size();
+    if (size >= L) {
+      result = valid(i);
+    }
+    buf_.push_back(i);
+    return result;
+  }
+
+  unsigned long get_weakness(unsigned long v) {
+    std::size_t sum_begin = 0;
+    std::size_t sum_end = 0;
+    unsigned long sum = 0;
+    while (sum != v) {
+      if (sum < v) {
+        assert(sum_end != buf_.size());
+        sum += buf_[sum_end];
+        ++sum_end;
+      }
+      if (sum > v) {
+        assert(sum_begin != buf_.size());
+        sum -= buf_[sum_begin];
+        ++sum_begin;
+      }
+    }
+    std::cout << "sum_begin = " << sum_begin << " sum_end = " << sum_end
+              << "\n";
+    std::vector<unsigned long> vec(buf_.begin() + sum_begin,
+                                   buf_.begin() + sum_end);
+    std::sort(vec.begin(), vec.end());
+    return vec[0] + vec[vec.size() - 1];
+  }
+
+private:
+  bool valid(unsigned long v) const {
+    assert(buf_.size() >= L);
+    for (auto i = buf_.size() - 25; i != buf_.size(); ++i) {
+      for (auto j = i + 1; j != buf_.size(); ++j) {
+        if (v == buf_[i] + buf_[j]) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  std::vector<unsigned long> buf_;
+};
+
+int main(int argc, char **argv) {
+  Buffer<25> buf;
+  unsigned long invalid = 0;
+  for (std::string line; std::getline(std::cin, line);) {
+    if (!buf.add_value(line)) {
+      if (invalid == 0) {
+        invalid = std::stoul(line);
+      }
+    }
+  }
+
+  std::cout << "First Invalid: " << invalid << "\n";
+  std::cout << "Weakness: " << buf.get_weakness(invalid) << "\n";
+  return 0;
+}