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Author: ivanmmarkovic

Ch02. Analysis/anagramDetectionExtraSpace.py

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+'''
+this solution is O(n),
+but it requires extra space for 2 lists
+'''
+
+def anagramDetection(string1, string2):
+    l1 = [0] * 26
+    l2 = [0] * 26
+
+    pos1 = 0
+    while pos1 < len(string1):
+        character = string1[pos1]
+        index = ord(character) - ord("a")
+        l1[index] = l1[index] + 1
+        pos1 += 1
+
+    pos2 = 0
+    while pos2 < len(string2):
+        character = string2[pos2]
+        index = ord(character) - ord("a")
+        l2[index] = l2[index] + 1
+        pos2 += 1
+
+    pos = 0
+    isAnagram = True
+    while pos < len(l1) and isAnagram:
+        if l1[pos] != l2[pos]:
+            isAnagram = False
+        else:
+            pos += 1
+
+    return isAnagram
+
+print(anagramDetection("python", "typhon"))
+print(anagramDetection("baba", "abba"))
+print(anagramDetection("babb", "abba"))

Ch02. Analysis/anagramDetectionOn2.py

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+
+# loop inside loop - O(n2)
+
+def anagramDetection(string1, string2):
+    l2 = list(string2)
+    isAnagram = True
+    pos1 = 0
+    while pos1 < len(string1) and isAnagram:
+        character = string1[pos1]
+
+        characterFound = False
+        pos2 = 0
+        while pos2 < len(l2) and not characterFound:
+            if character == l2[pos2]:
+                l2[pos2] = None
+                characterFound = True
+            else:
+                pos2 += 1
+
+        if not characterFound:
+            isAnagram = False
+        else:
+            pos1 += 1
+
+    return isAnagram
+
+print(anagramDetection("python", "typhon"))
+print(anagramDetection("baba", "abba"))
+print(anagramDetection("babb", "abba"))

Ch02. Analysis/anagramDetectionSorting.py

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+'''
+you might think that this algorithm is O(n) but,
+sorting is dominant part of algorithm and
+sorting is typically either O(n2) or O(nlogn)
+'''
+
+
+def anagramDetection(string1, string2):
+    l1 = list(string1)
+    l2 = list(string2)
+
+    l1.sort()
+    l2.sort()
+
+    isAnagram = True
+    pos = 0
+    while pos < len(l1) and isAnagram:
+        if l1[pos] == l2[pos]:
+            pos += 1
+        else:
+            isAnagram = False
+
+
+    return isAnagram
+
+print(anagramDetection("python", "typhon"))
+print(anagramDetection("baba", "abba"))
+print(anagramDetection("babb", "abba"))

Ch02. Analysis/sumOfNumbers.py

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+
+# iterative solution
+def sumOfNumbersIterative(number):
+    sum = 0
+    for item in range(number + 1):
+        sum += item
+    return sum
+
+
+print(sumOfNumbersIterative(5))
+
+# non-iterative solution
+def sumOfNumbersNonIterative(number):
+    return number * (number + 1) / 2
+
+print(sumOfNumbersNonIterative(5))
+