Python/dynamic_programming/all_construct.py
Sailesh Shrestha 3815a97575
Add all_construct dynamic programming implementation (#5626)
* Add all_construct dynamic programming implementation

* all_construct: remove the main function

* all_construct: Add type hints

* all_construct: changed map to list comprehension,fix mutable default arguments

* all_construct: fixed type hints

* all_construct: cleaner code for initializing word_bank argument

* all_construct: added an import for annotations

* all_construct: added None in the argument with word_bank

* all_construct: fixed a type hint

* all_construct: Fixed some more type hints
2021-11-04 16:18:38 +01:00

59 lines
1.9 KiB
Python

"""
Program to list all the ways a target string can be
constructed from the given list of substrings
"""
from __future__ import annotations
def all_construct(target: str, word_bank: list[str] | None = None) -> list[list[str]]:
"""
returns the list containing all the possible
combinations a string(target) can be constructed from
the given list of substrings(word_bank)
>>> all_construct("hello", ["he", "l", "o"])
[['he', 'l', 'l', 'o']]
>>> all_construct("purple",["purp","p","ur","le","purpl"])
[['purp', 'le'], ['p', 'ur', 'p', 'le']]
"""
word_bank = word_bank or []
# create a table
table_size: int = len(target) + 1
table: list[list[list[str]]] = []
for i in range(table_size):
table.append([])
# seed value
table[0] = [[]] # because empty string has empty combination
# iterate through the indices
for i in range(table_size):
# condition
if table[i] != []:
for word in word_bank:
# slice condition
if target[i : i + len(word)] == word:
new_combinations: list[list[str]] = [
[word] + way for way in table[i]
]
# adds the word to every combination the current position holds
# now,push that combination to the table[i+len(word)]
table[i + len(word)] += new_combinations
# combinations are in reverse order so reverse for better output
for combination in table[len(target)]:
combination.reverse()
return table[len(target)]
if __name__ == "__main__":
print(all_construct("jwajalapa", ["jwa", "j", "w", "a", "la", "lapa"]))
print(all_construct("rajamati", ["s", "raj", "amat", "raja", "ma", "i", "t"]))
print(
all_construct(
"hexagonosaurus",
["h", "ex", "hex", "ag", "ago", "ru", "auru", "rus", "go", "no", "o", "s"],
)
)