Added older advents

advent_of_code_2018/day2/main2.cc

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+#include <algorithm>
+#include <iostream>
+#include <string>
+#include <vector>
+
+using namespace std;
+
+size_t label_diff(string const &lhs, string const &rhs)
+{
+    size_t diff = 0;
+    for (size_t idx = 0; idx != lhs.size(); ++idx)
+        diff += lhs[idx] - rhs[idx] ? 1 : 0;
+    return diff;
+}
+
+string equal_part(string const &lhs, string const &rhs)
+{
+    string rval;
+    rval.reserve(lhs.size() - 1);
+
+    for (size_t idx = 0; idx != lhs.size(); ++idx)
+    {
+        if (lhs[idx] == rhs[idx])
+            rval.push_back(lhs[idx]);
+    }
+    
+    return rval;
+}
+
+int main()
+{
+    size_t dubbles = 0;
+    size_t tripples = 0;
+
+    string buffer;
+    vector<string> labels;
+
+    while (getline(cin, buffer))
+        labels.push_back(buffer);
+
+    for (string const &lhs : labels)
+    {
+        for  (string const &rhs : labels)
+        {
+            size_t difference = label_diff(rhs, lhs);
+
+            if (difference == 1)
+            {
+                cout << "Equal part: " << equal_part(lhs, rhs) << "\n";
+                return 0;
+            }
+        }
+    }
+}
+
+//jbbenqtlaxhivmwyscjukztdp correct