Last ch. 4 problems

Author: jsgoller1

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

@@ -17,9 +17,27 @@ int ZeroOneRandom() {
 }
 
 int UniformRandom(int lower_bound, int upper_bound) {
-  // TODO - you fill in here.
-  return 0;
+  int bound = upper_bound - lower_bound;
+  int bound_copy = bound;
+  int bits_needed = 0;
+  while (bound_copy) {
+    bound_copy >>= 1;
+    bits_needed++;
+  }
+  while (true) {
+    int guess = 0;
+    for (int i = 0; i < bits_needed; i++) {
+      guess <<= 1;
+      if (ZeroOneRandom()) {
+        guess |= 1;
+      }
+    }
+    if (guess <= bound) {
+      return guess;
+    }
+  }
 }
+
 bool UniformRandomRunner(TimedExecutor& executor, int lower_bound,
                          int upper_bound) {
   using namespace test_framework;

elements-of-programming-interviews/problem_mapping.js

@@ -142,7 +142,7 @@ problem_mapping = {
         },
         "4.10 Generate uniform random numbers": {
             "C++: uniform_random_number.cc": {
-                "passed": 0,
+                "passed": 7,
                 "total": 7
             },
             "Java: UniformRandomNumber.java": {
@@ -164,7 +164,7 @@ problem_mapping = {
                 "total": 10000
             },
             "Python: rectangle_intersection.py": {
-                "passed": 0,
+                "passed": 10000,
                 "total": 10000
             }
         }

elements-of-programming-interviews/python/rectangle_intersection.py

@@ -6,9 +6,41 @@
 Rect = collections.namedtuple('Rect', ('x', 'y', 'width', 'height'))
 
 
+def left(rect):
+    return rect.x
+
+
+def right(rect):
+    return rect.x + rect.width
+
+
+def down(rect):
+    return rect.y
+
+
+def up(rect):
+    return rect.y + rect.height
+
+
+def interval_overlap(x, l, r):
+    return l <= x <= r
+
+
+def line_overlap(a1, a2, b1, b2):
+    return interval_overlap(a1, b1, b2) or \
+        interval_overlap(a2, b1, b2) or \
+        interval_overlap(b1, a1, a2) or \
+        interval_overlap(b2, a1, a2)
+
+
 def intersect_rectangle(r1: Rect, r2: Rect) -> Rect:
-    # TODO - you fill in here.
-    return Rect(0, 0, 0, 0)
+    if not (line_overlap(left(r1), right(r1), left(r2), right(r2)) and
+            line_overlap(down(r1), up(r1), down(r2), up(r2))):
+        return Rect(0, 0, -1, -1)
+
+    x_vals = sorted([left(r1), right(r1), left(r2), right(r2)])
+    y_vals = sorted([up(r1), down(r1), up(r2), down(r2)])
+    return Rect(x_vals[1], y_vals[1], x_vals[2] - x_vals[1], y_vals[2] - y_vals[1])
 
 
 def intersect_rectangle_wrapper(r1, r2):
@@ -26,6 +58,11 @@ def fmt(x):
 
 
 if __name__ == '__main__':
+    """
+    r1 = Rect(76, 9, 12, 14)
+    r2 = Rect(20, 1, 62, 60)
+    # print(interval_overlap(up(r1), down(r2), up(r2)))
+    """
     exit(
         generic_test.generic_test_main('rectangle_intersection.py',
                                        'rectangle_intersection.tsv',