Merge branch 'master' of https://github.com/ben-xD/leet

Author: StBogdan

README.md

@@ -11,16 +11,16 @@
 |   5 	| [Bit Manipulation](chapter_5)       	|   8  	|   8   	|         	|
 |   6 	| [Math and Logic Puzzles](chapter_6) 	|  10  	|   10  	|    4    	|
 |   7 	| [OO Design](chapter_7)              	|   0  	|   12  	|         	|
-|   8 	| [Recursion and DP](chapter_8)       	|  12  	|   14  	|         	|
+|   8 	| [Recursion and DP](chapter_8)       	|  14  	|   14  	|         	|
 |   9 	| [System Design](chapter_9)          	|   0  	|   8   	|         	|
 |  10 	| [Sorting and Searching](chapter_10) 	|   9  	|   11  	|    1    	|
 |  11 	| [Testing](chapter_11)                	|   4  	|   6   	|    4    	|
 |  12 	| [C/C++](chapter_12)                  	|  11  	|   11  	|    11   	|
 |  13 	| [Java](chapter_13)                   	|   0  	|   8   	|         	|
 |  14 	| [Databases](chapter_14)              	|   0  	|   7   	|         	|
 |  15 	| [Threads and Locks](chapter_15)      	|   0  	|   7   	|         	|
-|  16 	| [Moderate](chapter_16)               	|  21  	|   26  	|    1    	|
-|  17 	| [Hard](chapter_17)                   	|  20  	|   26  	|         	|
+|  16 	| [Moderate](chapter_16)               	|  26  	|   26  	|    1    	|
+|  17 	| [Hard](chapter_17)                   	|  26  	|   26  	|         	|
 
 
 ### Schedule

chapter_8/p8_14.py

@@ -0,0 +1,50 @@
+from functools import lru_cache, partial
+from typing import List
+
+
+@lru_cache(None)
+def count_eval(form: str, result: bool):
+    if len(form) == 1:
+        literal = int(form)
+        return 1 if bool(literal) == result else 0
+
+    ways = 0
+    for i in range(0, len(form)-1, 2):
+        current_op = form[i+1]
+        left_side = partial(count_eval, form[:i+1])
+        right_side = partial(count_eval, form[i+2:])
+
+        if current_op == "&":
+            if result == True:
+                ways += left_side(True) * right_side(True)
+            else:
+                ways += left_side(False) * right_side(True) \
+                    + left_side(True) * right_side(False) \
+                    + left_side(False) * right_side(False)
+        elif current_op == "^":
+            if result == False:
+                ways += left_side(False) * right_side(False) \
+                    + left_side(True) * right_side(True)
+            else:
+                ways += left_side(True) * right_side(False) \
+                    + left_side(False) * right_side(True)
+        elif current_op == "|":
+            if result == False:
+                ways += left_side(False) * right_side(False)
+            else:
+                ways += left_side(True) * right_side(True) \
+                    + left_side(False) * right_side(True) \
+                    + left_side(True) * right_side(False)
+        
+    # print(f"Looking to package {form} for {result}, ways for this {ways}")
+    return ways
+
+if __name__ == "__main__":
+    exs = [
+        ("1^0", True),
+        ("1^0|0|1", False),
+        ("0&0&0&1^1|0", True)
+    ]
+
+    for formula, target in exs:
+        print(f"Ways to partition {formula} for {target} are {count_eval(formula, target)}")

chapter_8/p8_4.py

@@ -0,0 +1,23 @@
+from typing import List
+
+
+def gen_subsets(set_elems: List[int], offset: int):
+    if offset == len(set_elems) - 1:
+        return [[set_elems[offset]], []]
+
+    wo_elem = gen_subsets(set_elems, offset+1)
+    w_elem = [[set_elems[offset]] +
+              subset for subset in gen_subsets(set_elems, offset+1)]
+    return w_elem + wo_elem
+
+
+if __name__ == "__main__":
+    exs = [
+        [1, 2, 3],
+        [1],
+        [1, 2, 3, 4]
+    ]
+
+    for arr in exs:
+        subsets = gen_subsets(arr, 0)
+        print(f"Subsets of {arr} are size {len(subsets)}:  {subsets}")