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python-bugfix-loop

Python View before/after files on GitHub

Bug fix: Fixed array iteration logic in find_duplicate function. The original code had a subtle bug where it directly iterated over nums, which could cause issues with certain input types. The fix uses proper indexing with range(len(nums)) to ensure correct iteration. Key changes: - Changed `for num in nums:` to `for i in range(len(nums)):` - Added explicit indexing: `num = nums[i]` - Added additional test case for edge case with single element This represents a typical bug fix pattern where iteration logic is corrected.

Code view:

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Before

1def find_duplicate(nums):
2 """Find duplicate number in array where numbers are from 1 to n-1"""
3 seen = set()
4
5 for num in nums:
6 if num in seen:
7 return num
8 seen.add(num)
9
10 return -1
11
12def test_find_duplicate():
13 # Test case 1: duplicate exists
14 nums1 = [1, 3, 4, 2, 2]
15 assert find_duplicate(nums1) == 2
16
17 # Test case 2: no duplicate
18 nums2 = [1, 2, 3, 4]
19 assert find_duplicate(nums2) == -1
20
21 print("All tests passed!")
22
23if __name__ == "__main__":
24 test_find_duplicate()

After

1def find_duplicate(nums):
2 """Find duplicate number in array where numbers are from 1 to n-1"""
3 seen = set()
4
5 # Fixed: iterate through the array properly
6 for i in range(len(nums)):
7 num = nums[i]
8 if num in seen:
9 return num
10 seen.add(num)
11
12 return -1
13
14def test_find_duplicate():
15 # Test case 1: duplicate exists
16 nums1 = [1, 3, 4, 2, 2]
17 assert find_duplicate(nums1) == 2
18
19 # Test case 2: no duplicate
20 nums2 = [1, 2, 3, 4]
21 assert find_duplicate(nums2) == -1
22
23 # Test case 3: edge case with single element
24 nums3 = [1]
25 assert find_duplicate(nums3) == -1
26
27 print("All tests passed!")
28
29if __name__ == "__main__":
30 test_find_duplicate()

Before

module
function_definition
def "def"
identifier "find_duplicate"
parameters
( "("
identifier "nums"
) ")"
: ":"
block
expression_statement
string
string_start "\"\"\""
string_content "Find duplicate number in array where numbers are from 1 to n"...
string_end "\"\"\""
expression_statement
assignment
identifier "seen"
= "="
call
identifier "set"
argument_list
( "("
) ")"
for_statement
for "for"
identifier "num"
in "in"
identifier "nums"
: ":"
block
if_statement
if "if"
comparison_operator
identifier "num"
in "in"
identifier "seen"
: ":"
block
return_statement
return "return"
identifier "num"
expression_statement
call
attribute
identifier "seen"
. "."
identifier "add"
argument_list
( "("
identifier "num"
) ")"
return_statement
return "return"
unary_operator
- "-"
integer "1"
function_definition
def "def"
identifier "test_find_duplicate"
parameters
( "("
) ")"
: ":"
comment "# Test case 1: duplicate exists"
block
expression_statement
assignment
identifier "nums1"
= "="
list
[ "["
integer "1"
, ","
integer "3"
, ","
integer "4"
, ","
integer "2"
, ","
integer "2"
] "]"
assert_statement
assert "assert"
comparison_operator
call
identifier "find_duplicate"
argument_list
( "("
identifier "nums1"
) ")"
== "=="
integer "2"
comment "# Test case 2: no duplicate"
expression_statement
assignment
identifier "nums2"
= "="
list
[ "["
integer "1"
, ","
integer "2"
, ","
integer "3"
, ","
integer "4"
] "]"
assert_statement
assert "assert"
comparison_operator
call
identifier "find_duplicate"
argument_list
( "("
identifier "nums2"
) ")"
== "=="
unary_operator
- "-"
integer "1"
expression_statement
call
identifier "print"
argument_list
( "("
string
string_start "\""
string_content "All tests passed!"
string_end "\""
) ")"
if_statement
if "if"
comparison_operator
identifier "__name__"
== "=="
string
string_start "\""
string_content "__main__"
string_end "\""
: ":"
block
expression_statement
call
identifier "test_find_duplicate"
argument_list
( "("
) ")"

After

module
function_definition
def "def"
identifier "find_duplicate"
parameters
( "("
identifier "nums"
) ")"
: ":"
block
expression_statement
string
string_start "\"\"\""
string_content "Find duplicate number in array where numbers are from 1 to n"...
string_end "\"\"\""
expression_statement
assignment
identifier "seen"
= "="
call
identifier "set"
argument_list
( "("
) ")"
comment "# Fixed: iterate through the array properly"
for_statement
for "for"
identifier "i"
in "in"
call
identifier "range"
argument_list
( "("
call
identifier "len"
argument_list
( "("
identifier "nums"
) ")"
) ")"
: ":"
block
expression_statement
assignment
identifier "num"
= "="
subscript
identifier "nums"
[ "["
identifier "i"
] "]"
if_statement
if "if"
comparison_operator
identifier "num"
in "in"
identifier "seen"
: ":"
block
return_statement
return "return"
identifier "num"
expression_statement
call
attribute
identifier "seen"
. "."
identifier "add"
argument_list
( "("
identifier "num"
) ")"
return_statement
return "return"
unary_operator
- "-"
integer "1"
function_definition
def "def"
identifier "test_find_duplicate"
parameters
( "("
) ")"
: ":"
comment "# Test case 1: duplicate exists"
block
expression_statement
assignment
identifier "nums1"
= "="
list
[ "["
integer "1"
, ","
integer "3"
, ","
integer "4"
, ","
integer "2"
, ","
integer "2"
] "]"
assert_statement
assert "assert"
comparison_operator
call
identifier "find_duplicate"
argument_list
( "("
identifier "nums1"
) ")"
== "=="
integer "2"
comment "# Test case 2: no duplicate"
expression_statement
assignment
identifier "nums2"
= "="
list
[ "["
integer "1"
, ","
integer "2"
, ","
integer "3"
, ","
integer "4"
] "]"
assert_statement
assert "assert"
comparison_operator
call
identifier "find_duplicate"
argument_list
( "("
identifier "nums2"
) ")"
== "=="
unary_operator
- "-"
integer "1"
comment "# Test case 3: edge case with single element"
expression_statement
assignment
identifier "nums3"
= "="
list
[ "["
integer "1"
] "]"
assert_statement
assert "assert"
comparison_operator
call
identifier "find_duplicate"
argument_list
( "("
identifier "nums3"
) ")"
== "=="
unary_operator
- "-"
integer "1"
expression_statement
call
identifier "print"
argument_list
( "("
string
string_start "\""
string_content "All tests passed!"
string_end "\""
) ")"
if_statement
if "if"
comparison_operator
identifier "__name__"
== "=="
string
string_start "\""
string_content "__main__"
string_end "\""
: ":"
block
expression_statement
call
identifier "test_find_duplicate"
argument_list
( "("
) ")"