Finally, create a main loop to process the input commands.
- The program starts by initializing an empty tree (root = None).
- It reads the number of operations, then enters a loop to process each command one by one.
- Inside the loop, it parses the operation type and key from the input line.
- Based on the operation, it calls the appropriate function (insert, find, succ, or pred).
- Handle return values carefully: insert may change the root, and successor/predecessor should print "null" when no value exists.
# --- Main Program Logic ---
root = __________
num_operations = int(input())
for _ in range(num_operations):
line = input().strip().split()
op, key = line[0], int(line[1])
if op == "ins":
root = __________(root, key)
elif op == "find":
result = __________(root, key)
print(str(result).lower())
elif op == "succ":
result = __________(root, key)
print(__________ if __________ is not __________ else "__________")
elif op == "pred":
# TODO: Call predecessor and print result
result = __________(root, key)
print(__________ if __________ is not __________ else "__________")
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