Tasks Details
medium
1.
Peaks
Divide an array into the maximum number of same-sized blocks, each of which should contain an index P such that A[P - 1] < A[P] > A[P + 1].
Task Score
36%
Correctness
50%
Performance
20%
A non-empty array A consisting of N integers is given.
A peak is an array element which is larger than its neighbors. More precisely, it is an index P such that 0 < P < N − 1, A[P − 1] < A[P] and A[P] > A[P + 1].
For example, the following array A:
A[0] = 1 A[1] = 2 A[2] = 3 A[3] = 4 A[4] = 3 A[5] = 4 A[6] = 1 A[7] = 2 A[8] = 3 A[9] = 4 A[10] = 6 A[11] = 2has exactly three peaks: 3, 5, 10.
We want to divide this array into blocks containing the same number of elements. More precisely, we want to choose a number K that will yield the following blocks:
- A[0], A[1], ..., A[K − 1],
- A[K], A[K + 1], ..., A[2K − 1],
...- A[N − K], A[N − K + 1], ..., A[N − 1].
What's more, every block should contain at least one peak. Notice that extreme elements of the blocks (for example A[K − 1] or A[K]) can also be peaks, but only if they have both neighbors (including one in an adjacent blocks).
The goal is to find the maximum number of blocks into which the array A can be divided.
Array A can be divided into blocks as follows:
- one block (1, 2, 3, 4, 3, 4, 1, 2, 3, 4, 6, 2). This block contains three peaks.
- two blocks (1, 2, 3, 4, 3, 4) and (1, 2, 3, 4, 6, 2). Every block has a peak.
- three blocks (1, 2, 3, 4), (3, 4, 1, 2), (3, 4, 6, 2). Every block has a peak. Notice in particular that the first block (1, 2, 3, 4) has a peak at A[3], because A[2] < A[3] > A[4], even though A[4] is in the adjacent block.
However, array A cannot be divided into four blocks, (1, 2, 3), (4, 3, 4), (1, 2, 3) and (4, 6, 2), because the (1, 2, 3) blocks do not contain a peak. Notice in particular that the (4, 3, 4) block contains two peaks: A[3] and A[5].
The maximum number of blocks that array A can be divided into is three.
Write a function:
def solution(A)
that, given a non-empty array A consisting of N integers, returns the maximum number of blocks into which A can be divided.
If A cannot be divided into some number of blocks, the function should return 0.
For example, given:
A[0] = 1 A[1] = 2 A[2] = 3 A[3] = 4 A[4] = 3 A[5] = 4 A[6] = 1 A[7] = 2 A[8] = 3 A[9] = 4 A[10] = 6 A[11] = 2the function should return 3, as explained above.
Write an efficient algorithm for the following assumptions:
- N is an integer within the range [1..100,000];
- each element of array A is an integer within the range [0..1,000,000,000].
Copyright 2009–2025 by Codility Limited. All Rights Reserved. Unauthorized copying, publication or disclosure prohibited.
Solution
Programming language used Python
Time spent on task 6 minutes
Notes
not defined yet
Task timeline
Code: 10:23:43 UTC,
java,
autosave
Code: 10:23:53 UTC,
py,
autosave
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
#print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
for block in range(block_num):
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
Code: 10:24:03 UTC,
py,
verify,
result: Passed
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
#print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
for block in range(block_num):
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
User test case 1:
[1, 3, 2, 1]
User test case 2:
[5]
Analysis
expand all
User tests
1.
0.036 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Traceback (most recent call last):
File "exec.py", line 129, in <module>
main()
File "exec.py", line 91, in main
result = solution( A )
File "/tmp/solution.py", line 27, in solution
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
IndexError: list index out of range
1.
0.036 s
OK
function result: 0
function result: 0
Code: 10:24:28 UTC,
py,
verify,
result: Passed
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
#print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
for block in range(block_num):
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
User test case 1:
[1, 3, 2, 1]
User test case 2:
[5]
Analysis
expand all
User tests
1.
0.036 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Traceback (most recent call last):
File "exec.py", line 129, in <module>
main()
File "exec.py", line 91, in main
result = solution( A )
File "/tmp/solution.py", line 27, in solution
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
IndexError: list index out of range
1.
0.036 s
OK
function result: 0
function result: 0
Code: 10:24:38 UTC,
py,
autosave
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
for block in range(block_num):
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
Code: 10:24:39 UTC,
py,
verify,
result: Passed
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
for block in range(block_num):
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
User test case 1:
[1, 3, 2, 1]
User test case 2:
[5]
Analysis
expand all
User tests
1.
0.036 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Traceback (most recent call last):
File "exec.py", line 129, in <module>
main()
File "exec.py", line 91, in main
result = solution( A )
File "/tmp/solution.py", line 27, in solution
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
IndexError: list index out of range
stdout:
[1]
1.
0.036 s
OK
function result: 0
function result: 0
Code: 10:25:00 UTC,
py,
verify,
result: Passed
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
print(block_num)
for block in range(block_num):
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
User test case 1:
[1, 3, 2, 1]
User test case 2:
[5]
Analysis
expand all
User tests
1.
0.036 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Traceback (most recent call last):
File "exec.py", line 129, in <module>
main()
File "exec.py", line 91, in main
result = solution( A )
File "/tmp/solution.py", line 28, in solution
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
IndexError: list index out of range
stdout:
[1] 2
1.
0.036 s
OK
function result: 0
function result: 0
Code: 10:26:12 UTC,
py,
autosave
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
print(block_num, b)
for block in range(block_num):
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
Code: 10:26:17 UTC,
py,
verify,
result: Passed
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
print(block_num, possible)
for block in range(block_num):
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
User test case 1:
[1, 3, 2, 1]
User test case 2:
[5]
Analysis
expand all
User tests
1.
0.036 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Traceback (most recent call last):
File "exec.py", line 129, in <module>
main()
File "exec.py", line 91, in main
result = solution( A )
File "/tmp/solution.py", line 28, in solution
if block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
IndexError: list index out of range
stdout:
[1] 2 0
1.
0.036 s
OK
function result: 0
function result: 0
Code: 10:27:46 UTC,
py,
autosave
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
print(block_num, possible)
for block in range(block_num):
if peakblock * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
Code: 10:27:57 UTC,
py,
autosave
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
print(block_num, possible)
for block in range(block_num):
if peak_length >block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
Code: 10:28:04 UTC,
py,
verify,
result: Passed
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
print(block_num, possible)
for block in range(block_num):
if peak_length >= block and block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
User test case 1:
[1, 3, 2, 1]
User test case 2:
[5]
Analysis
expand all
User tests
1.
0.036 s
RUNTIME ERROR,
tested program terminated with exit code 1
stderr:
Traceback (most recent call last):
File "exec.py", line 129, in <module>
main()
File "exec.py", line 91, in main
result = solution( A )
File "/tmp/solution.py", line 28, in solution
if peak_length >= block and block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
IndexError: list index out of range
stdout:
[1] 2 0
1.
0.036 s
OK
function result: 0
function result: 0
Code: 10:28:22 UTC,
py,
autosave
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
print(block_num, possible)
for block in range(block_num):
if peak_length > block and block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
Code: 10:28:22 UTC,
py,
verify,
result: Passed
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
print(block_num, possible)
for block in range(block_num):
if peak_length > block and block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
User test case 1:
[1, 3, 2, 1]
User test case 2:
[5]
Analysis
expand all
User tests
1.
0.036 s
OK
function result: 1
function result: 1
stdout:
[1] 2 0
1.
0.036 s
OK
function result: 0
function result: 0
Code: 10:28:49 UTC,
py,
verify,
result: Passed
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
print(block_num, possible)
for block in range(block_num):
if peak_length > block and block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
User test case 1:
[1, 3, 2, 1]
User test case 2:
[5]
Analysis
expand all
User tests
1.
0.040 s
OK
function result: 1
function result: 1
stdout:
[1] 2 0
1.
0.040 s
OK
function result: 0
function result: 0
Code: 10:29:09 UTC,
py,
verify,
result: Passed
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
print(block_num, possible)
for block in range(block_num):
if peak_length > block and block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
User test case 1:
[1, 3, 2, 1]
User test case 2:
[5]
Analysis
expand all
User tests
1.
0.052 s
OK
function result: 1
function result: 1
stdout:
[1] 2 0
1.
0.056 s
OK
function result: 0
function result: 0
Code: 10:29:18 UTC,
py,
autosave
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
#print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
print(block_num, possible)
for block in range(block_num):
if peak_length > block and block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
Code: 10:29:25 UTC,
py,
verify,
result: Passed
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
#print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
#print(block_num, possible)
for block in range(block_num):
if peak_length > block and block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1
User test case 1:
[1, 3, 2, 1]
User test case 2:
[5]
Analysis
Code: 10:29:27 UTC,
py,
final,
score:
36
def solution(A):
length = len(A)
peak_array = []
for i, _ in enumerate(A):
if i - 1 < 0:
continue
if i + 1 >= length:
continue
if A[i-1] < A[i] and A[i+1] < A[i]:
peak_array.append(i)
peak_length = len(peak_array)
if peak_length == 0: return 0
#print(peak_array)
for peak in peak_array:
block_num , possible = divmod(length, peak + 1 )
if possible != 0:
continue
count = 0
#print(block_num, possible)
for block in range(block_num):
if peak_length > block and block * (peak + 1) <= peak_array[block] <= block * (peak + 1) + peak:
count += 1
if count == block_num:
#print("block num ::: " + str(block_num + 1))
return block_num
else:
break
return 1Analysis summary
The following issues have been detected: wrong answers.
For example, for the input [0, 1, 0, 0, 1, 0, 0, 1, 0] the solution returned a wrong answer (got 1 expected 3).
Analysis
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
1.
0.036 s
WRONG ANSWER,
got 1 expected 7
1.
0.036 s
WRONG ANSWER,
got 1 expected 4
2.
0.036 s
OK
3.
0.036 s
OK
4.
0.036 s
OK
1.
0.036 s
WRONG ANSWER,
got 1 expected 4
2.
0.036 s
WRONG ANSWER,
got 1 expected 3
expand all
Performance tests
1.
0.044 s
WRONG ANSWER,
got 1 expected 625
2.
0.044 s
WRONG ANSWER,
got 1 expected 100
1.
0.048 s
OK
1.
0.112 s
WRONG ANSWER,
got 1 expected 5000
2.
0.096 s
WRONG ANSWER,
got 1 expected 1250
1.
0.148 s
OK
2.
0.172 s
WRONG ANSWER,
got 1 expected 30030
1.
0.192 s
WRONG ANSWER,
got 1 expected 25000
2.
0.156 s
OK