Added older advents

advent_of_code_2019/day2/main2.cc

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+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+vector<int> read_input()
+{
+    vector<int> rval;
+    int buffer;
+    char comma;
+
+    while (cin)
+    {
+        cin >> buffer;
+        rval.push_back(buffer);
+        cin >> comma;
+    }
+
+    return rval;
+}
+
+int run_program(vector<int> program, int noun = 12, int verb = 2)
+{
+    cout << "running program!\n";
+    size_t instruction = 0;
+
+    program[1] = noun;
+    program[2] = verb;
+
+    while(true)
+    {
+        switch(program[instruction++])
+        {
+            case 1:
+            {
+                size_t lhs = program[instruction++];
+                size_t rhs = program[instruction++];
+                size_t result = program[instruction++];
+                program[result] = program[lhs] + program[rhs];
+            }
+            break;
+
+            case 2:
+            {
+                size_t lhs = program[instruction++];
+                size_t rhs = program[instruction++];
+                size_t result = program[instruction++];
+                program[result] = program[lhs] * program[rhs];
+            }
+            break;
+
+            case 99:
+                return program[0];
+        }
+    }
+}
+
+int main(int argc, char *argv[])
+{
+    vector<int> program = read_input();
+    int target_output = 19690720;
+
+    for (int noun = 0; noun < 100; ++noun)
+    {
+        cout << "\rIteration: " << noun << " / 100";
+        for (int verb = 0; verb < 100; ++verb)
+        {
+            int result = run_program(program, noun, verb);
+            
+            if (result == target_output)
+            {
+                cout << "Noun: " << noun << "\n";
+                cout << "Verb: " << verb << "\n";
+                cout << "Answer: " << (100 * noun + verb) << "\n";
+                return 0;
+            }
+        }
+    }
+}