Added some solutions for Advent of Code.

aoc2015/P02.cpp

@@ -0,0 +1,11 @@
+// Replace 'x' with ' ' in input.
+int main() {
+  LL answer1 = 0, sides[3], answer2 = 0;
+  while(cin >> sides[0] >> sides[1] >> sides[2]) {
+    sort(sides, &(sides[3]));
+    answer1 += 3*sides[0]*sides[1] + 2*sides[0]*sides[2] + 2*sides[2]*sides[1];
+    answer2 += 2*(sides[0]+sides[1]) + sides[0]*sides[1]*sides[2];
+  }
+  cout << "Answer 1: " << answer1 << endl;
+  cout << "Answer 2: " << answer2 << endl;
+}

aoc2015/P03.cpp

@@ -0,0 +1,30 @@
+int main() {
+  set<PI> seen;
+  PI p(0,0), q(0,0);
+  seen.insert(p);
+  GS(s);
+  FORUI(s.size()) {
+    char c = s[i];
+    switch(c) {
+    case '>':
+      p.XX++;
+      break;
+    case '<':
+      p.XX--;
+      break;
+    case '^':
+      p.YY--;
+      break;
+    case 'v':
+      p.YY++;
+      break;
+    default:
+      die();
+    }
+    if(seen.find(p) == seen.end()) {
+      seen.insert(p);
+    }
+    swap(p,q); // For part 2, include this line.
+  }
+  cout << "Answer: " << seen.size() << endl;
+}