多层循环与组合数

1. 二层循环与 (n2)

如 (52)=10

c, n = 0, 5for i in range(n):    for j in range(i+1, n):        c += 1c        # 10
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2. 三层循环与 (n3)

如 (103)=120

c, n = 0, 10for i in range(n):    for j in range(i+1, n):        for k in range(j+1, n):            c += 1c            # 120
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