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ankit167ankit167
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Merge pull request keon#83 from ankit167/Binary_Search_fix
Added comments, main() and fixed pep8 errors
2 parents 8fbc8be + 7594178 commit 7fb80b9

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-56
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3 files changed

+90
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‎search/binary_search.py‎

Lines changed: 22 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -1,3 +1,9 @@
1+
#
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# Binary search works for a sorted array.
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# Note: The code logic is written for an array sorted in
4+
# increasing order.
5+
# T(n): O(log n)
6+
#
17

28

39
def binary_search(array, query):
@@ -13,14 +19,19 @@ def binary_search(array, query):
1319
hi = mid - 1
1420
return None
1521

16-
array = [1,2,3,3,3,3,4,4,4,4,5,6]
17-
print(array)
18-
print("-----SEARCH-----")
19-
print("found: ", 5, " in index:" , binary_search(array, 5))
20-
print("-----SEARCH-----")
21-
print("found: ", 6, " in index:" , binary_search(array, 6))
22-
print("-----SEARCH-----")
23-
print("found: ", 7, " in index:" , binary_search(array, 7))
24-
print("-----SEARCH-----")
25-
print("found: ", -1, " in index:" , binary_search(array, -1))
26-
print("-----SEARCH-----")
22+
23+
def main():
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array = [1, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 6]
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print(array)
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print("-----SEARCH-----")
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print("found: ", 5, " in index:", binary_search(array, 5))
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print("-----SEARCH-----")
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print("found: ", 6, " in index:", binary_search(array, 6))
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print("-----SEARCH-----")
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print("found: ", 7, " in index:", binary_search(array, 7))
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print("-----SEARCH-----")
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print("found: ", -1, " in index:", binary_search(array, -1))
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print("-----SEARCH-----")
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36+
if __name__ == "__main__":
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main()

‎search/first_occurance.py‎

Lines changed: 33 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -1,33 +1,45 @@
1+
#
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# Find first occurance of a number in a sorted array (increasing order)
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# Approach- Binary Search
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# T(n)- O(log n)
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#
6+
7+
18
def firstOccurance(array, query):
29
lo, hi = 0, len(array) - 1
310
while lo <= hi:
411
mid = lo + (hi-lo) // 2
512
print("lo: ", lo, " hi: ", hi, " mid: ", mid)
613
if (mid == 0 and array[mid] == query) or \
7-
(array[mid] == query and array[mid-1] < query):
14+
(array[mid] == query and array[mid-1] < query):
815
return mid
916
elif array[mid] <= query:
1017
lo = mid + 1
1118
else:
1219
hi = mid - 1
1320

14-
array = [1,2,3,3,3,3,4,4,4,4,5,6,6,6]
15-
print(array)
16-
print("-----SEARCH-----")
17-
query = 3
18-
print("found first: ", query, " in index:" , firstOccurance(array, query))
19-
print("-----SEARCH-----")
20-
query = 5
21-
print("found first: ", query, " in index:" , firstOccurance(array, query))
22-
print("-----SEARCH-----")
23-
query = 7
24-
print("found first: ", query, " in index:" , firstOccurance(array, query))
25-
print("-----SEARCH-----")
26-
query = 1
27-
print("found first: ", query, " in index:" , firstOccurance(array, query))
28-
print("-----SEARCH-----")
29-
query = -1
30-
print("found first: ", query, " in index:" , firstOccurance(array, query))
31-
print("-----SEARCH-----")
32-
query = 9
33-
print("found first: ", query, " in index:" , firstOccurance(array, query))
21+
22+
def main():
23+
array = [1, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 6, 6, 6]
24+
print(array)
25+
print("-----SEARCH-----")
26+
query = 3
27+
print("found first: ", query, " in index:", firstOccurance(array, query))
28+
print("-----SEARCH-----")
29+
query = 5
30+
print("found first: ", query, " in index:", firstOccurance(array, query))
31+
print("-----SEARCH-----")
32+
query = 7
33+
print("found first: ", query, " in index:", firstOccurance(array, query))
34+
print("-----SEARCH-----")
35+
query = 1
36+
print("found first: ", query, " in index:", firstOccurance(array, query))
37+
print("-----SEARCH-----")
38+
query = -1
39+
print("found first: ", query, " in index:", firstOccurance(array, query))
40+
print("-----SEARCH-----")
41+
query = 9
42+
print("found first: ", query, " in index:", firstOccurance(array, query))
43+
44+
if __name__ == "__main__":
45+
main()

‎search/last_occurance.py‎

Lines changed: 35 additions & 24 deletions
Original file line numberDiff line numberDiff line change
@@ -1,36 +1,47 @@
1+
#
2+
# Find last occurance of a number in a sorted array (increasing order)
3+
# Approach- Binary Search
4+
# T(n)- O(log n)
5+
#
6+
7+
18
def lastOccurance(array, query):
29
lo, hi = 0, len(array) - 1
310
while lo <= hi:
411
mid = lo + (hi - lo) // 2
512
if (array[mid] == query and mid == len(array)-1) or \
613
(array[mid] == query and array[mid+1] > query):
7-
return mid
14+
return mid
815
elif (array[mid] <= query):
916
lo = mid + 1
1017
else:
1118
hi = mid - 1
1219

1320

14-
array = [1,2,3,3,3,3,4,4,4,4,5,6,6,6]
15-
print(array)
16-
print("-----SEARCH-----")
17-
query = 3
18-
print("found last: ", query, " in index:" , lastOccurance(array, query))
19-
print("-----SEARCH-----")
20-
query = 5
21-
print("found last: ", query, " in index:" , lastOccurance(array, query))
22-
print("-----SEARCH-----")
23-
query = 7
24-
print("found last: ", query, " in index:" , lastOccurance(array, query))
25-
print("-----SEARCH-----")
26-
query = 1
27-
print("found last: ", query, " in index:" , lastOccurance(array, query))
28-
print("-----SEARCH-----")
29-
query = -1
30-
print("found last: ", query, " in index:" , lastOccurance(array, query))
31-
print("-----SEARCH-----")
32-
query = 9
33-
print("found last: ", query, " in index:" , lastOccurance(array, query))
34-
print("-----SEARCH-----")
35-
query = 6
36-
print("found last: ", query, " in index:" , lastOccurance(array, query))
21+
def main():
22+
array = [1, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 6, 6, 6]
23+
print(array)
24+
print("-----SEARCH-----")
25+
query = 3
26+
print("found last: ", query, " in index:", lastOccurance(array, query))
27+
print("-----SEARCH-----")
28+
query = 5
29+
print("found last: ", query, " in index:", lastOccurance(array, query))
30+
print("-----SEARCH-----")
31+
query = 7
32+
print("found last: ", query, " in index:", lastOccurance(array, query))
33+
print("-----SEARCH-----")
34+
query = 1
35+
print("found last: ", query, " in index:", lastOccurance(array, query))
36+
print("-----SEARCH-----")
37+
query = -1
38+
print("found last: ", query, " in index:", lastOccurance(array, query))
39+
print("-----SEARCH-----")
40+
query = 9
41+
print("found last: ", query, " in index:", lastOccurance(array, query))
42+
print("-----SEARCH-----")
43+
query = 6
44+
print("found last: ", query, " in index:", lastOccurance(array, query))
45+
46+
if __name__ == "__main__":
47+
main()

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