RandomGenerator: Optimize randintExcept()

Author: adazem009

src/engine/internal/randomgenerator.cpp

@@ -47,10 +47,23 @@ long RandomGenerator::randintExcept(long start, long end, long except) const
     if (start > end) {
         std::swap(start, end);
     }
-    std::uniform_int_distribution<long> distribution(start, end);
-    long value = distribution(*m_generator);
-    if (value == except) {
-        return randintExcept(start, end, except);
+
+    if (except < start || except > end) {
+        return randint(start, end);
+    } else if (start == end) {
+        return start;
+    } else if (end - start == 1) {
+        if (except == start)
+            return end;
+        else
+            return start;
+    }
+
+    if (randint(0, 1) == 0) {
+        std::uniform_int_distribution<long> distribution(start, except - 1);
+        return distribution(*m_generator);
+    } else {
+        std::uniform_int_distribution<long> distribution(except + 1, end);
+        return distribution(*m_generator);
     }
-    return value;
 }

test/randomgenerator/randomgenerator_test.cpp

@@ -64,4 +64,36 @@ TEST(RandomGeneratorTest, RandIntExcept)
         ASSERT_LE(num, 5);
         ASSERT_NE(num, 2);
     }
+
+    for (int i = 0; i < 25; i++) {
+        num = rng->randintExcept(5, 8, 2);
+        ASSERT_GE(num, 5);
+        ASSERT_LE(num, 8);
+    }
+
+    for (int i = 0; i < 25; i++) {
+        num = rng->randintExcept(5, 8, 10);
+        ASSERT_GE(num, 5);
+        ASSERT_LE(num, 8);
+    }
+
+    for (int i = 0; i < 25; i++) {
+        num = rng->randintExcept(2, 2, 2);
+        ASSERT_EQ(num, 2);
+    }
+
+    for (int i = 0; i < 25; i++) {
+        num = rng->randintExcept(2, 2, 5);
+        ASSERT_EQ(num, 2);
+    }
+
+    for (int i = 0; i < 25; i++) {
+        num = rng->randintExcept(1, 2, 1);
+        ASSERT_EQ(num, 2);
+    }
+
+    for (int i = 0; i < 25; i++) {
+        num = rng->randintExcept(1, 2, 2);
+        ASSERT_EQ(num, 1);
+    }
 }