avl_tree.h: adding more test, fixing more bugs

src/lol/algorithm/avl_tree.h

@@ -171,8 +171,8 @@ protected:
 
         void compute_balance()
         {
-            this->m_stairs_lo = this->m_lo ? this->m_lo->m_stairs_lo + this->m_lo->m_stairs_hi + 1 : 0;
-            this->m_stairs_hi = this->m_hi ? this->m_hi->m_stairs_lo + this->m_hi->m_stairs_hi + 1 : 0;
+            this->m_stairs_lo = this->m_lo ? lol::max(this->m_lo->m_stairs_lo, this->m_lo->m_stairs_hi) + 1 : 0;
+            this->m_stairs_hi = this->m_hi ? lol::max(this->m_hi->m_stairs_lo, this->m_hi->m_stairs_hi) + 1 : 0;
         }
 
         int get_balance()

src/t/algorithm/avl_tree.cpp

@@ -12,6 +12,8 @@
 
 #include <lol/engine-internal.h>
 
+#include <lol/algorithm/avl_tree.h>
+
 #include <lolunit.h>
 
 namespace lol
@@ -60,6 +62,9 @@ lolunit_declare_fixture(AvlTreeTest)
 
         lolunit_assert_equal(tree.insert(-1, 1), true);
         lolunit_assert_equal(tree.get_root_balance(), -1);
+
+        lolunit_assert_equal(tree.insert(-2, 1), true);
+        lolunit_assert_equal(tree.get_root_balance(), 0);
     }
 };