Completed all Data Structure Exercises

Algorithms/1_BinarySearch/1.py

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+# ### Binary Search Exercise
+# 1. When I try to find number 5 in below list using binary search, it doesn't work and returns me -1 index. Why is that?
+
+#     ```numbers = [1,4,6,9,10,5,7]```
+
+# This is because the array is not sorted in order from lowest to highest. 
+# Once it splits the first time, it starts looking in the [1,4,6] range and doesn't find 5
+
+# 1. Find index of all the occurances of a number from sorted list
+
+#     ```
+#     numbers = [1,4,6,9,11,15,15,15,17,21,34,34,56]
+#     number_to_find = 15  
+#     ```
+#    This should return 5,6,7 as indices containing number 15 in the array
+
+from util import time_it
+
+@time_it
+def linear_search(numbers_list, number_to_find):
+    for index, element in enumerate(numbers_list):
+        if element == number_to_find:
+            return index
+    return -1
+
+@time_it
+def binary_search(numbers_list, number_to_find):
+    left_index = 0
+    right_index = len(numbers_list) - 1
+    mid_index = 0
+
+    while left_index <= right_index:
+        mid_index = (left_index + right_index) // 2
+        mid_number = numbers_list[mid_index]
+
+        if mid_number == number_to_find:
+            return mid_index
+
+        if mid_number < number_to_find:
+            left_index = mid_index + 1
+        else:
+            right_index = mid_index - 1
+
+    return -1
+
+def binary_search_recursive(numbers_list, number_to_find, left_index, right_index):
+    if right_index < left_index:
+        return -1
+
+    mid_index = (left_index + right_index) // 2
+    if mid_index >= len(numbers_list) or mid_index < 0:
+        return -1
+
+    mid_number = numbers_list[mid_index]
+
+    if mid_number == number_to_find:
+        return mid_index
+
+    if mid_number < number_to_find:
+        left_index = mid_index + 1
+    else:
+        right_index = mid_index - 1
+
+    return binary_search_recursive(numbers_list, number_to_find, left_index, right_index)
+
+#this should run the binary search, find the index, and then recursively run the search on both the right and left side
+def binary_search_multiple(numbers_list, number_to_find):
+
+    index = binary_search(numbers_list,number_to_find)
+    result_indices = [index]
+
+    # find all indices on the left
+    i = index - 1
+    while i>=0:
+        if numbers_list[i] == numbers_list[index]:
+            result_indices.append(i)
+        else:
+            break
+        i = i-1
+
+    # find all indices on the right
+    i = index + 1
+    while i<len(numbers_list):
+        if numbers_list[i] == numbers_list[index]:
+            result_indices.append(i)
+        else:
+            break
+        i = i+1
+
+    return sorted(result_indices)
+
+numbers_list = [12, 15, 17, 19, 21, 21, 21, 21, 24, 45, 67]
+number_to_find = 21
+
+index = binary_search_multiple(numbers_list, number_to_find)
+print(f"Number found at index {index} using binary search")
+
+numbers = [1,4,6,9,11,15,15,15,15,17,21,34,34,56]
+number_to_find = 15
+
+index = binary_search_multiple(numbers, number_to_find)
+print(f"Number found at index {index} using binary search")
+
+#Lesson: I was approaching it wrong. If something isn't working, scratch the approach. 
+#Lesson #2: Try the simplest solution first. Although in this case it's a bit ugly since you're just doing a linear search after your binary search

Algorithms/1_BinarySearch/binary_search_exercise.md

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+### Binary Search Exercise
+1. When I try to find number 5 in below list using binary search, it doesn't work and returns me -1 index. Why is that?
+
+    ```numbers = [1,4,6,9,10,5,7]```
+
+1. Find index of all the occurances of a number from sorted list
+
+    ```
+    numbers = [1,4,6,9,11,15,15,15,17,21,34,34,56]
+    number_to_find = 15  
+    ```
+   This should return 5,6,7 as indices containing number 15 in the array
+
+[Solution](https://github.com/codebasics/data-structures-algorithms-python/blob/master/algorithms/1_BinarySearch/binary_search_exercise_solution.py)    

Algorithms/1_BinarySearch/binarysearch.py

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+from util import time_it
+
+@time_it
+def linear_search(numbers_list, number_to_find):
+    for index, element in enumerate(numbers_list):
+        if element == number_to_find:
+            return index
+    return -1
+
+@time_it
+def binary_search(numbers_list, number_to_find):
+    left_index = 0
+    right_index = len(numbers_list) - 1
+    mid_index = 0
+
+    while left_index <= right_index:
+        mid_index = (left_index + right_index) // 2
+        mid_number = numbers_list[mid_index]
+
+        if mid_number == number_to_find:
+            return mid_index
+
+        if mid_number < number_to_find:
+            left_index = mid_index + 1
+        else:
+            right_index = mid_index - 1
+
+    return -1
+
+def binary_search_recursive(numbers_list, number_to_find, left_index, right_index):
+    if right_index < left_index:
+        return -1
+
+    mid_index = (left_index + right_index) // 2
+    if mid_index >= len(numbers_list) or mid_index < 0:
+        return -1
+
+    mid_number = numbers_list[mid_index]
+
+    if mid_number == number_to_find:
+        return mid_index
+
+    if mid_number < number_to_find:
+        left_index = mid_index + 1
+    else:
+        right_index = mid_index - 1
+
+    return binary_search_recursive(numbers_list, number_to_find, left_index, right_index)
+
+numbers_list = [12, 15, 17, 19, 21, 24, 45, 67]
+number_to_find = 21
+
+index = binary_search_recursive(numbers_list, number_to_find, 0, len(numbers_list))
+print(f"Number found at index {index} using binary search")
+

Algorithms/1_BinarySearch/util.py

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+import time
+def time_it(func):
+    def wrapper(*args, **kwargs):
+        start = time.time()
+        result = func(*args,**kwargs)
+        end = time.time()
+        print(func.__name__ +" took " + str((end-start)*1000) + " mil sec")
+        return result
+    return wrapper

Data_Structures/10_Graph/graph.py

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+class Graph:
+    def __init__(self, edges):
+        self.edges = edges
+        self.graph_dict = {}
+        for start, end in edges:
+            if start in self.graph_dict:
+                self.graph_dict[start].append(end)
+            else:
+                self.graph_dict[start] = [end]
+        print("Graph Dict:", self.graph_dict)
+
+    def get_paths(self, start, end, path=[]):
+        path = path + [start]
+
+        if start == end:
+            return [path]
+
+        if start not in self.graph_dict:
+            return []
+
+        paths = []
+        for node in self.graph_dict[start]:
+            if node not in path:
+                new_paths = self.get_paths(node, end, path)
+                for p in new_paths:
+                    paths.append(p)
+
+        return paths
+
+    def get_shortest_path(self, start, end, path=[]):
+        path = path + [start]
+
+        if start == end:
+            return path
+
+        if start not in self.graph_dict:
+            return None
+
+        shortest_path = None
+        for node in self.graph_dict[start]:
+            if node not in path:
+                sp = self.get_shortest_path(node, end, path)
+                if sp:
+                    if shortest_path is None or len(sp) < len(shortest_path):
+                        shortest_path = sp
+
+        return shortest_path
+
+if __name__ == '__main__':
+
+    routes = [
+        ("Mumbai","Pune"),
+        ("Mumbai", "Surat"),
+        ("Surat", "Bangaluru"),
+        ("Pune","Hyderabad"),
+        ("Pune","Mysuru"),
+        ("Hyderabad","Bangaluru"),
+        ("Hyderabad", "Chennai"),
+        ("Mysuru", "Bangaluru"),
+        ("Chennai", "Bangaluru")
+    ]
+
+    routes = [
+        ("Mumbai", "Paris"),
+        ("Mumbai", "Dubai"),
+        ("Paris", "Dubai"),
+        ("Paris", "New York"),
+        ("Dubai", "New York"),
+        ("New York", "Toronto"),
+    ]
+
+    route_graph = Graph(routes)
+
+    start = "Mumbai"
+    end = "New York"
+
+    print(f"All paths between: {start} and {end}: ",route_graph.get_paths(start,end))
+    print(f"Shortest path between {start} and {end}: ", route_graph.get_shortest_path(start,end))
+
+    start = "Dubai"
+    end = "New York"
+
+    print(f"All paths between: {start} and {end}: ",route_graph.get_paths(start,end))
+    print(f"Shortest path between {start} and {end}: ", route_graph.get_shortest_path(start,end))

Data_Structures/2_Arrays/2-1.py

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+# # Exercise: Array DataStructure
+
+# 1. Let us say your expense for every month are listed below,
+# 	1. January -  2200
+#  	2. February - 2350
+#     3. March - 2600
+#     4. April - 2130
+#     5. May - 2190
+
+# Create a list to store these monthly expenses and using that find out,
+
+#     1. In Feb, how many dollars you spent extra compare to January?
+#     2. Find out your total expense in first quarter (first three months) of the year.
+#     3. Find out if you spent exactly 2000 dollars in any month
+#     4. June month just finished and your expense is 1980 dollar. Add this item to our monthly expense list
+#     5. You returned an item that you bought in a month of April and
+#     got a refund of 200$. Make a correction to your monthly expense list
+#     based on this
+
+expenses = [2200,2350,2600,2130,2190]
+
+# 1. In Feb, how many dollars you spent extra compare to January?
+
+extraSpend = expenses[1] - expenses[0]
+
+print(f"In February, you spent ${extraSpend} more than in January")
+
+# 2. Find out your total expense in first quarter (first three months) of the year.
+
+q1_expenses = sum(expenses[0:3])
+
+print(f"In Q1, you spent ${q1_expenses}")
+
+# 3. Find out if you spent exactly 2000 dollars in any month
+
+print("Did I spent 2000$ in any month? ", 2000 in expenses) # False
+
+did_i_spend = False
+
+for e in expenses:
+    if e == 2000:
+        did_i_spend = True
+
+if did_i_spend == True:
+    print('You did spend exactly 2000 in a month')
+else:
+    print('You did not spend exactly 2000 in a month')
+
+#4. June month just finished and your expense is 1980 dollar. Add this item to our monthly expense list
+
+expenses.append(1980)
+
+print(expenses)
+
+#  5. You returned an item that you bought in a month of April and
+# #     got a refund of 200$. Make a correction to your monthly expense list
+# #     based on this
+
+expenses[3] = expenses[3] - 200
+print(expenses)

Data_Structures/2_Arrays/2-2.py

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+# 2. You have a list of your favourite marvel super heros.
+# ```
+# heros=['spider man','thor','hulk','iron man','captain america']
+# ```
+
+# Using this find out,
+
+#     1. Length of the list
+#     2. Add 'black panther' at the end of this list
+#     3. You realize that you need to add 'black panther' after 'hulk',
+#        so remove it from the list first and then add it after 'hulk'
+#     4. Now you don't like thor and hulk because they get angry easily :)
+#        So you want to remove thor and hulk from list and replace them with doctor strange (because he is cool).
+#        Do that with one line of code.
+#     5. Sort the heros list in alphabetical order (Hint. Use dir() functions to list down all functions available in list)
+
+
+heros=['spider man','thor','hulk','iron man','captain america']
+
+# 1. Length of the list
+print("length of heros list:",len(heros))
+
+# 2. Add 'black panther' at the end of this list
+
+heros.append('black panther')
+print(heros)
+
+# 3. You realize that you need to add 'black panther' after 'hulk',
+# so remove it from the list first and then add it after 'hulk'
+
+heros.remove('black panther')
+heros.insert(3,'black panther')
+print(heros)
+
+# 4. Now you don't like thor and hulk because they get angry easily :)
+# So you want to remove thor and hulk from list and replace them with doctor strange (because he is cool).
+# Do that with one line of code.
+
+heros[1:3] = ['doctor stranger']
+print(heros)
+
+# 5. Sort the heros list in alphabetical order (Hint. Use dir() functions to list down all functions available in list)
+
+heros.sort()
+print(heros)
+
+

Data_Structures/2_Arrays/2-3.py

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+# 3. Create a list of all odd numbers between 1 and a max number.
+# Max number is something you need to take from a user using input() function
+
+odd_numbers_list = []
+
+max_number = int(input('What is the max number? '))
+
+for i in range(0,max_number+1):
+    if i%2 != 0:
+        odd_numbers_list.append(i)
+
+print(odd_numbers_list)
+