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Single Right rotation (compare to RotateWithLeftChild page 148 text) void rotateRight(AVLNode *& curr) { AVLNode * kid = curr->left; curr->left = kid->right;

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Presentation on theme: "Single Right rotation (compare to RotateWithLeftChild page 148 text) void rotateRight(AVLNode *& curr) { AVLNode * kid = curr->left; curr->left = kid->right;"— Presentation transcript:

1 Single Right rotation (compare to RotateWithLeftChild page 148 text) void rotateRight(AVLNode *& curr) { AVLNode * kid = curr->left; curr->left = kid->right; kid->right = curr; curr->height = max(height(curr->left), height(curr->right)) + 1; kid>height = max(height(kid->left), height(kid->right)) + 1 curr = kid; }

2 Why did we need to pass the root by *& ? If you want the value of an int to change, you pass it by reference. If you want the value of a POINTER to change, you pass the pointer by reference. You can pass the address of an int to a routine and change the value of the int. But passing an address DOES NOT allow you to change the address itself, unless you pass it by reference.

3 Pass by value doit(int x) {x = 10; cout << “doit x” << x; } main() { int x; x = 5; doit(x); cout << “main x “ << x; } x x x100 0x200

4 Pass by address doit(int *x) {*x = 10; cout << “doit x” << *x; } main() { int x; x = 5; doit( &x); cout << “main x “ << x; } x x x100 0x200

5 Pass by reference doit(int &x) { x = 10; cout << “doit x” << x; } main() { int x; x = 5; doit( x); cout << “main x “ << x; } x x x100 0x200 Similar to pass by address, but the compiler does all the work for you.

6 Pass by value with pointers doit(int *x) {x = new int(); *x = 27 cout << “doit x” << x << *x; } main() { int * x = NULL; doit(x); cout << “main x “ << x <<*x; } x x NULL NULL 0x300 0x100 0x200 0x300 27

7 Pass by address with pointers doit(int **x) {*x = new int(); **x = 27 cout << “doit x” << *x << **x; } main() { int * x = NULL; doit(&x); cout << “main x “ << x <<*x; } x x NULL 0x300 0x100 0x200 0x300 27

8 Pass by pointer reference doit(int * &x) { x = new int(); *x = 27 cout << “doit x” << x << *x; } main() { int * x = NULL; doit( x); cout << “main x “ << x <<*x; } x x NULL 0x300 0x100 0x200 0x300 27

9 Assigning pointers – simply copies contents (addresses) int * t = new int (); *t = 15; int * s = t; int ** addr = &t; *addr = new int(); t s 0x200 0x300 0x400 0x x400 0x700 addr 0x200 0x500

10 So what about rotateRight? void rotateRight(AVLNode *& curr) { AVLNode * kid = curr->left; curr->left = kid->right; kid->right = curr; curr->height = max(height(curr->left), height(curr->right)) + 1; kid>height = max(height(kid->left), height(kid- >right)) + 1 curr = kid; } 0x x400 0x320 0x2000x80 0x200 0x320 0x curr 0x100 When the calling routine passes in root->left, the compiler records the ADDRESS of the root’s left pointer (which is 0x100 in our case). kid0x320 curr

11 So what about rotateRight? void rotateRight(AVLNode *& curr) { AVLNode * kid = curr->left; curr->left = kid->right; kid->right = curr; curr->height = max(height(curr->left), height(curr->right)) + 1; kid>height = max(height(kid->left), height(kid- >right)) + 1 curr = kid; } 0x x400 0x320 0x2000x80 0x x x curr 0x100 When the calling routine passes in root->left, the compiler records the ADDRESS of the root’s left pointer (which is 0x100 in our case). kid0x320 curr

12 WARNING: If the calling routine passes in a COPY of the address (say temp pointed to 0x200), only the COPY is changed. In our case, the only pointer to node 15 is changed.


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