Added older advents

advent_of_code_2019/day4/main1.cc

@@ -0,0 +1,41 @@
+#include <iostream>
+#include <string>
+
+using namespace std;
+
+bool meets_criteria(size_t passwd)
+{
+    string number = to_string(passwd);
+
+    bool adjacent = false;
+
+    char min = '0';
+    char prev = '1';
+    for (char ch : number)
+    {
+        adjacent = adjacent | (prev == ch);
+        
+        if (ch < min)
+            return false;
+        
+        min = ch;
+        prev = ch;
+    }
+
+    return adjacent;
+}
+
+int main()
+{
+    const size_t LOWER = 178416;
+    const size_t UPPER = 676461;
+
+    size_t valid = 0;
+    for (size_t idx = LOWER; idx <= UPPER; ++idx)
+    {
+        if (meets_criteria(idx))
+            ++valid;
+    }
+
+    cout << "valid: " << valid << "\n";
+}

advent_of_code_2019/day4/main2.cc

@@ -0,0 +1,62 @@
+#include <iostream>
+#include <string>
+
+using namespace std;
+
+bool meets_criteria(size_t passwd)
+{
+    string number = to_string(passwd);
+
+    bool adjacent = false;
+    int groupsize = 0;
+
+    char min = '0';
+    char prev = '1';
+    for (char ch : number)
+    {
+        adjacent = adjacent | (prev == ch);
+        
+        if (prev == ch)
+            ++groupsize;
+        else
+        {
+            if (groupsize > 1 && groupsize % 2 != 0)
+            {
+                cout << "groupsize bounced: " << passwd << "\n";
+                return false; //uneven group
+            }
+            
+            prev = ch;
+            groupsize = 1;
+        }
+
+        if (ch < min)
+            return false;
+        
+        min = ch;
+    }
+
+    if (groupsize == 1)
+        return adjacent;
+    else if (groupsize % 2 != 0)
+    {
+        cout << "groupsize bounced (end): " << passwd << "\n";
+        return false;
+    }
+    return true;
+}
+
+int main()
+{
+    const size_t LOWER = 178416;
+    const size_t UPPER = 676461;
+
+    size_t valid = 0;
+    for (size_t idx = LOWER; idx <= UPPER; ++idx)
+    {
+        if (meets_criteria(idx))
+            ++valid;
+    }
+
+    cout << "valid: " << valid << "\n";
+}