Created
March 15, 2013 08:09
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AVL rebalancing
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| def get_bal(left, right): return left - right | |
| node = stack[i] | |
| cbal = get_bal(node[1], node[2]) | |
| if abs(cbal) < 2: break | |
| rel_side = cbal / (cbal % 2) #-1 or 1, left /right | |
| side = ((1 + rel_side) / 2) + 1 # 1 or 2, left / right | |
| child = node[side] | |
| gcbal = get_bal(child[1], child[2]) | |
| if (rel_side * gcbal) > 0: | |
| # right rotate right or left rotate left, see below | |
| grandchild = child[other_side] | |
| grandchild[side] = child | |
| child[other_side] = child[other_side][side] | |
| node[side] = child[other_side] | |
| child = node[side] | |
| if i == 0: | |
| self.root = child | |
| else: | |
| parent = stack[i - 1] | |
| if parent[1] is node: | |
| parent[1] = child | |
| elif parent[2] is node: | |
| parent[2] = child | |
| node[side] = child[other_side] | |
| child[other_side] = node | |
| node = parent if i > 0 else self.root | |
| # update gc heights, c heights, self height # 7 total? maybe just 4. | |
| node[side][other_side][side] = node[side] # RLR = R -OR- LRL = L | |
| node[side][other_side] = node[side][other_side][side] # RL = RLR -OR- LR = LRL | |
| node[side] = node[side][other_side] # R = RL -OR- L = LR |
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