Python: Find the number of combinations
Python Basic - 1: Exercise-62 with Solution
Write a Python program to find the number of combinations that satisfy p + q + r + s = n where n is a given number <= 4000 and p, q, r, s in the range of 0 to 1000.
from collections import Counter print("Input a positive integer: (ctrl+d to exit)") pair_dict = Counter() for i in range(2001): pair_dict[i] = min(i, 2000 - i) + 1 while True: try: n = int(input()) ans = 0 for i in range(n + 1): ans += pair_dict[i] * pair_dict[n - i] print("Number of combinations of a,b,c,d:",ans) except EOFError: break
Input a positive integer: (ctrl+d to exit) 252 Number of combinations of a,b,c,d: 2731135
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