1 files changed, 119 insertions, 0 deletions
diff --git a/day13/part2.cpp b/day13/part2.cpp
new file mode 100644
index 0000000..3ecf8d2
--- /dev/null
+++ b/day13/part2.cpp
@@ -0,0 +1,119 @@
+#include <iostream>
+#include <string>
+#include <vector>
+
+int consumeInt(std::string& s)
+{
+    int n = 0;
+    int i;
+
+    for (i = 0; s[i] >= '0' && s[i] <= '9'; ++i)
+        n = n * 10 + s[i] - '0';
+
+    s = s.substr(i);
+    return n;
+}
+
+int compare(std::string left, std::string right)
+{
+    int lt = 0, rt = 0;
+
+    while (left.size() != 0 && right.size() != 0) {
+        if (left[0] == ']') {
+            if (right[0] != ']') {
+                return 1;
+            }
+            if (rt) --rt;
+            else right = right.substr(1);
+            left = left.substr(1);
+        } else if (right[0] == ']') {
+            if (left[0] != ']') {
+                return 0;
+            }
+            if (lt) --lt;
+            else left = left.substr(1);
+            right = right.substr(1);
+        } else if (left[0] == '[') {
+            if (right[0] != '[')
+                ++rt;
+            else
+                right = right.substr(1);
+            left = left.substr(1);
+        } else if (right[0] == '[') {
+            if (left[0] != '[')
+                ++lt;
+            else
+                left = left.substr(1);
+            right = right.substr(1);
+        } else {
+            int ln = consumeInt(left);
+            int rn = consumeInt(right);
+
+            if (ln < rn) {
+                return 1;
+            } else if (ln > rn) {
+                return 0;
+            }
+
+            while (rt) {
+                if (left[0] != ']') {
+                    return 0;
+                }
+
+                left = left.substr(1);
+                --rt;
+            }
+            while (lt) {
+                if (right[0] != ']') {
+                    return 1;
+                }
+
+                right = right.substr(1);
+                --lt;
+            }
+        }
+
+        bool lcomma = left[0] == ',';
+        if (lcomma) {
+            left = left.substr(1);
+            if (right[0] != ',') {
+                return 0;
+            }
+        }
+        if (right[0] == ',') {
+            right = right.substr(1);
+            if (!lcomma) {
+                return 1;
+            }
+        }
+    }
+
+    if (left.size() == 0 && right.size() == 0)
+        return 1;
+    else
+        return 0;
+}
+
+int main()
+{
+    std::string line;
+    int lt2 = 0;
+    int lt6 = 0;
+
+    while (1) {
+        std::getline(std::cin, line);
+        if (std::cin.eof())
+            break;
+        if (line.empty())
+            continue;
+
+        if (compare(line, "[[2]]"))
+            lt2++;
+        if (compare(line, "[[6]]"))
+            lt6++;
+    }
+
+    std::cout << "lt2: " << lt2 + 1 << " lt6: " << lt6 + 2 << std::endl;
+    std::cout << "product: " << (lt2 + 1) * (lt6 + 2) << std::endl;
+}
+