czcbangkai

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║     Logic      ║             Flip Binary Tree             ║        Reverse Singly Linked List        ║
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║ Base Case      ║ Root is empty                            ║ Head is empty                            ║
║                ║ Root has no left child                   ║ Head has no next node                    ║
║ Recursive Call ║ Call root.left to get the final new root ║ Call head.next to get the final new head ║
║ Current Call   ║ Let root.left.right point to root        ║ Let head.next.next point to head         ║
║                ║ Let root.left.left point to root.right   ║                                          ║
║                ║ Let root.left point to NULL              ║ Let head.next point to NULL              ║
║                ║ Let root.right point to NULL             ║