Tasks Details
easy
1.
Brackets
Determine whether a given string of parentheses (multiple types) is properly nested.
Task Score
100%
Correctness
100%
Performance
100%
A string S consisting of N characters is considered to be properly nested if any of the following conditions is true:
- S is empty;
- S has the form "(U)" or "[U]" or "{U}" where U is a properly nested string;
- S has the form "VW" where V and W are properly nested strings.
For example, the string "{[()()]}" is properly nested but "([)()]" is not.
Write a function:
def solution(S)
that, given a string S consisting of N characters, returns 1 if S is properly nested and 0 otherwise.
For example, given S = "{[()()]}", the function should return 1 and given S = "([)()]", the function should return 0, as explained above.
Write an efficient algorithm for the following assumptions:
- N is an integer within the range [0..200,000];
- string S is made only of the following characters: '(', '{', '[', ']', '}' and/or ')'.
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used Python
Time spent on task 17 minutes
Notes
not defined yet
Code: 08:32:46 UTC,
java,
autosave
Analysis
expand all
Example tests
1.
0.036 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Traceback (most recent call last): File "exec.py", line 123, in <module> main() File "exec.py", line 64, in main sol = __import__('solution') File "/tmp/solution.py", line 6 for i in xrange(len(S)) ^ SyntaxError: invalid syntax
1.
0.040 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Traceback (most recent call last): File "exec.py", line 123, in <module> main() File "exec.py", line 64, in main sol = __import__('solution') File "/tmp/solution.py", line 6 for i in xrange(len(S)) ^ SyntaxError: invalid syntax
Analysis
expand all
Example tests
1.
0.036 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Traceback (most recent call last): File "exec.py", line 123, in <module> main() File "exec.py", line 85, in main result = solution( S ) File "/tmp/solution.py", line 6, in solution for i in xrange(len(S)): NameError: name 'xrange' is not defined
1.
0.036 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Traceback (most recent call last): File "exec.py", line 123, in <module> main() File "exec.py", line 85, in main result = solution( S ) File "/tmp/solution.py", line 6, in solution for i in xrange(len(S)): NameError: name 'xrange' is not defined
Analysis
expand all
Example tests
1.
0.036 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Invalid result type, int expected, <class 'NoneType'> found.stdout:
0 1 2 3 4 5 6 7
1.
0.036 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Invalid result type, int expected, <class 'NoneType'> found.stdout:
0 1 2 3 4 5
Code: 08:43:25 UTC,
py,
autosave
Code: 08:43:36 UTC,
py,
autosave
Code: 08:44:07 UTC,
py,
autosave
Code: 08:44:20 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if S[i] is ")" and stack[size-1] is ""
Code: 08:44:34 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size
if S[i] is ")" and stack[size-1] is ""
Code: 08:44:47 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0
return
if S[i] is ")" and stack[size-1] is ""
Code: 08:44:57 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
if S[i] is ")" and stack[size-1] is ""
Code: 08:45:07 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is ""
Code: 08:45:18 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "("
size -=1
Code: 08:45:28 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif
Code: 08:45:40 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif S[i] is
Code: 08:46:11 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif S[i] is "{" and stack[size-1]
Code: 08:46:24 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif S[i] is "}" and stack[size-1] is ""
Code: 08:46:54 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif S[i] is "}" and stack[size-1] is "{":
size -=1
elif S[i] is "]" and stack[size-1] is
Code: 08:47:10 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif S[i] is "}" and stack[size-1] is "{":
size -=1
elif S[i] is "]" and stack[size-1] is "[":
size -=1
Code: 08:47:41 UTC,
py,
autosave
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif S[i] is "}" and stack[size-1] is "{":
size -=1
elif S[i] is "]" and stack[size-1] is "[":
size -=1
if size is 0
return 1
return
Code: 08:47:47 UTC,
py,
verify,
result: Passed
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif S[i] is "}" and stack[size-1] is "{":
size -=1
elif S[i] is "]" and stack[size-1] is "[":
size -=1
if size is 0:
return 1
return 0
Analysis
Code: 08:48:17 UTC,
py,
verify,
result: Passed
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif S[i] is "}" and stack[size-1] is "{":
size -=1
elif S[i] is "]" and stack[size-1] is "[":
size -=1
if size is 0:
return 1
return 0
Analysis
expand all
User tests
1.
0.001 s
RUNTIME ERROR,
invalid input, unexpected '(', expecting string
User test case 1:
((()()()))
Code: 08:48:30 UTC,
py,
verify,
result: Passed
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif S[i] is "}" and stack[size-1] is "{":
size -=1
elif S[i] is "]" and stack[size-1] is "[":
size -=1
if size is 0:
return 1
return 0
Code: 08:48:48 UTC,
py,
verify,
result: Passed
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif S[i] is "}" and stack[size-1] is "{":
size -=1
elif S[i] is "]" and stack[size-1] is "[":
size -=1
if size is 0:
return 1
return 0
Code: 08:48:50 UTC,
py,
final,
score: 
100
# you can write to stdout for debugging purposes, e.g.
# print("this is a debug message")
def solution(S):
stack = [0]*len(S)
size = 0
for i in range(len(S)):
if S[i] is "(" or S[i] is "{" or S[i] is "[":
stack[size] = S[i]
size += 1
else:
if size is 0:
return 0
elif S[i] is ")" and stack[size-1] is "(":
size -=1
elif S[i] is "}" and stack[size-1] is "{":
size -=1
elif S[i] is "]" and stack[size-1] is "[":
size -=1
if size is 0:
return 1
return 0
Analysis summary
The solution obtained perfect score.
Analysis
Detected time complexity:
O(N)
expand all
Correctness tests
1.
0.036 s
OK
2.
0.036 s
OK
3.
0.036 s
OK
4.
0.036 s
OK
5.
0.036 s
OK
1.
0.036 s
OK
1.
0.036 s
OK
2.
0.036 s
OK
3.
0.036 s
OK
4.
0.036 s
OK
5.
0.036 s
OK
expand all
Performance tests
1.
0.088 s
OK
2.
0.036 s
OK
3.
0.040 s
OK
1.
0.040 s
OK
2.
0.036 s
OK
3.
0.036 s
OK
1.
0.080 s
OK
multiple_full_binary_trees
sequence of full trees of the form T=(TT), depths [1..10..1], with/without some brackets at the end, length=49K+
sequence of full trees of the form T=(TT), depths [1..10..1], with/without some brackets at the end, length=49K+
✔
OK
1.
0.048 s
OK
2.
0.048 s
OK
3.
0.068 s
OK
4.
0.048 s
OK
5.
0.036 s
OK
broad_tree_with_deep_paths
string of the form [TTT...T] of 300 T's, each T being '{{{...}}}' nested 200-fold, length=120K+
string of the form [TTT...T] of 300 T's, each T being '{{{...}}}' nested 200-fold, length=120K+
✔
OK
1.
0.068 s
OK
2.
0.068 s
OK