More problems from chapter 2, moved around 2 and 1 to correct order

Author: Bogdan Stoicescu

.gitignore

@@ -3,4 +3,6 @@ graph_out/
 .vscode/
 settings.json
 
-*/__pycache__/*
+*/__pycache__/*
+.DS_Store
+Leet.egg-*/

README.md

@@ -1,3 +1,19 @@
 ## Cracking the Coding Interview (6th edition)
+
+### Current progress
+- Chapter 1: 9/9
+- Chapter 2: some/8
+- Chapter 10: 2/11
+
+### Schedule
 - Week 1: Chapter 4: Graphs and Trees
-- Week 2: Chapter 10: Sorting and Searching
+- Week 2: Chapter 10: Sorting and Searching
+- Week 3: Chapter 1: Arrays and Strings
+
+### Running the solutions
+
+For convenience, the project has a `setup.py` that specifies a package
+This can be installed locally in the virtualenvironment by using
+```bash
+pip install -e .
+```

chapter_2/linked_list_utils.py

@@ -7,7 +7,7 @@ def __init__(self, val, next_node=None):
         self. next = next_node
 
     def __str__(self):
-        return f"({self.val}) -> {self.next!r}"
+        return f"({self.val}) -> {self.next}"
 
 
 def link_list_of_list(arr) -> Node:
@@ -18,6 +18,9 @@ def link_list_of_list(arr) -> Node:
         now_elem = now_elem.next
     return head
 
+def llol(arr):
+    return link_list_of_list(arr)
+
 
 if __name__ == "__main__":
     ex1 = [1, 2, 3]

chapter_2/p2_1.py

@@ -1,26 +1,46 @@
-from linked_list_utils import *
+from chapter_2.linked_list_utils import Node, llol
 
 
-def k_to_last(k: int, h: Node):
-    ldr = h
-    folw = h
-    d = -1
+def remove_dups_ll(head: Node):
+    seen = set()
+    prev = None
+    while head:
+        if head.val in seen:
+            prev.next = head.next
+        else:
+            seen.add(head.val)
+        prev = head
+        head = head.next
 
-    while ldr:
-        print(f"Ldr is {ldr} and folw {folw}")
-        d += 1
-        if d > k:
-            folw = folw.next
-        ldr = ldr.next
 
-    if d<k:
-        raise Exception(f"Input too short for distance {d}")
-
-    return folw.val
+def remove_dups_nobuf(h: Node):
+    rc = h
+    while rc:
+        target = rc.val
+        prev = rc
+        restp = rc.next
+        while restp:
+            if restp.val == target:
+                prev.next = restp.next
+            else:
+                prev = restp
+            restp = restp.next
+        rc = rc.next
 
 
 if __name__ == "__main__":
-    ex1 = link_list_of_list([1, 2, 3, 4, 5, 6, 7])
-    d = 5
-    print(ex1)
-    print(k_to_last(d, ex1))
+    exs = [[1, 2, 3, 4, 5],
+           [11, 2, 3, 4, 5, 6, 11],
+           [11, 2, 3, 4, 5, 6, 11, 11, 11, 23],
+           [0],
+           [0, 0],
+           [1, 2, 1, 2, 1, 2, 1, 2, 1, 2, 2, 3, 1]]
+
+    for ex in exs:
+        r1 = llol(ex)
+        r2 = llol(ex)
+        remove_dups_nobuf(r1)
+        remove_dups_nobuf(r2)
+        print(f"For ex {ex} for ans 1: {r1}")
+        print(f"For ex {ex} for ans 2: {r2}")
+        print("-"*50)

chapter_2/p2_2.py

@@ -0,0 +1,26 @@
+from chapter_2.linked_list_utils import *
+
+
+def k_to_last(k: int, h: Node):
+    ldr = h
+    folw = h
+    d = -1
+
+    while ldr:
+        print(f"Ldr is {ldr} and folw {folw}")
+        d += 1
+        if d > k:
+            folw = folw.next
+        ldr = ldr.next
+
+    if d < k:
+        raise Exception(f"Input too short for distance {d}")
+
+    return folw.val
+
+
+if __name__ == "__main__":
+    ex1 = link_list_of_list([1, 2, 3, 4, 5, 6, 7])
+    d = 5
+    print(ex1)
+    print(k_to_last(d, ex1))

chapter_2/p2_3.py

@@ -0,0 +1,32 @@
+from chapter_2.linked_list_utils import llol, Node
+
+
+def remove_mid(mid_node: Node):
+    victim = mid_node.next
+    if not victim:
+        raise Exception("No following nodes")
+
+    # Take the value, and point to the next (can be none)
+    mid_node.val = victim.val
+    mid_node.next = victim.next
+    victim.next = None
+
+
+if __name__ == "__main__":
+    exs = [([1, 2, 3, 4, 5], 3),
+           ([1, 1, 1, 1], 1),
+           ([1, 2, 4, 5, 6, 7], 2),
+           ([1, 2, 3], 3)]
+
+    for arr, elem in exs:
+        head = llol(arr)
+        in_node = head
+        while in_node.val != elem:
+            in_node = in_node.next
+
+        try:
+            remove_mid(in_node)
+            print(f"For input {arr} to remove {elem} got result {head}")
+        except Exception as e:
+            print(f"For input {arr} to remove {elem} got error: {e}")
+        print("-"*50)

chapter_2/p2_4.py

@@ -0,0 +1,48 @@
+from chapter_2.linked_list_utils import llol, Node
+
+
+def part_around(x: int, head: Node):
+    low_head = None
+    high_head = None
+    low_root = None
+    high_root = None
+
+    elem_now = head
+    while elem_now:
+        elem_next = elem_now.next
+        if elem_now.val >= x:
+            if not high_root:
+                high_head = elem_now
+                high_root = elem_now
+            else:
+                high_head.next = elem_now
+                high_head = elem_now
+        else:
+            if not low_head:
+                low_head = elem_now
+                low_root = elem_now
+            else:
+                low_head.next = elem_now
+                low_head = elem_now
+        elem_now = elem_next
+
+    if low_root:
+        low_head.next = high_root  # Connect the parts
+        high_head.next = None
+        return low_root
+    else:
+        return high_root  # No low elems
+
+
+if __name__ == "__main__":
+    exs = [([1, 2, 3, 4, 5, 6, 7], 4),
+           ([10, 4, 7, 3, 1, 200, 40, 50, 3], 4),
+           ([30, 40, 50], 30),
+           ([1, 2, 5, 3, 2, 200], 3)
+           ]
+
+    for arr, x in exs:
+        head = llol(arr)
+        print(
+            f"For\t{head} around partition {x},\ngot\t{part_around(x, head)}")
+        print("-"*50)

setup.py

@@ -0,0 +1,7 @@
+from setuptools import setup, find_packages
+
+setup(
+    name='Leet',
+    version='0.0.1',
+    packages=find_packages(),
+)