Rectangle intersection

Author: jsgoller1

elements-of-programming-interviews/cpp/rectangle_intersection.cc

@@ -4,18 +4,51 @@
 #include "test_framework/generic_test.h"
 #include "test_framework/serialization_traits.h"
 struct Rect {
+  // x and y are bottom left corner
   int x, y, width, height;
 };
 
-Rect IntersectRectangle(const Rect& r1, const Rect& r2) {
-  // TODO - you fill in here.
-  return {0, 0, 0, 0};
-}
 bool operator==(const Rect& r1, const Rect& r2) {
   return std::tie(r1.x, r1.y, r1.width, r1.height) ==
          std::tie(r2.x, r2.y, r2.width, r2.height);
 }
 
+bool pointIntervalIntersect(const int p, const int l, const int r) {
+  // p in [l,r]?
+  return l <= p && p <= r;
+}
+
+bool cornerOverlap1D(const int aLeft, const int aRight, const int bLeft,
+                     const int bRight) {
+  return pointIntervalIntersect(bLeft, aLeft, aRight) ||
+         pointIntervalIntersect(bRight, aLeft, aRight) ||
+         pointIntervalIntersect(aLeft, bLeft, bRight) ||
+         pointIntervalIntersect(aRight, bLeft, bRight);
+}
+
+Rect IntersectRectangle(const Rect& r1, const Rect& r2) {
+  int r1Left = r1.x;
+  int r1Down = r1.y;
+  int r1Right = r1.x + r1.width;
+  int r1Up = r1.y + r1.height;
+
+  int r2Left = r2.x;
+  int r2Down = r2.y;
+  int r2Right = r2.x + r2.width;
+  int r2Up = r2.y + r2.height;
+
+  if (!(cornerOverlap1D(r1Left, r1Right, r2Left, r2Right) &&
+        cornerOverlap1D(r1Down, r1Up, r2Down, r2Up))) {
+    return {0, 0, -1, -1};
+  }
+  std::vector<int> yVals{r1Up, r1Down, r2Up, r2Down};
+  std::sort(yVals.begin(), yVals.end());
+  std::vector<int> xVals{r1Left, r1Right, r2Left, r2Right};
+  std::sort(xVals.begin(), xVals.end());
+
+  return {xVals[1], yVals[1], xVals[2] - xVals[1], yVals[2] - yVals[1]};
+}
+
 namespace test_framework {
 template <>
 struct SerializationTrait<Rect> : UserSerTrait<Rect, int, int, int, int> {

elements-of-programming-interviews/problem_mapping.js

@@ -156,7 +156,7 @@ problem_mapping = {
         },
         "4.11 Rectangle intersection": {
             "C++: rectangle_intersection.cc": {
-                "passed": 0,
+                "passed": 10000,
                 "total": 10000
             },
             "Java: RectangleIntersection.java": {