题解 | #24点游戏算法#

import sys

signs = ['+', '-', '*', '/']
precision = 0.00001
min24 = 24 - precision
max24 = 24 + precision

def compute24(n1, n2, n3, n4):
    for s1 in signs:
        for s2 in signs:
            for s3 in signs:
                    expr = "((" + n1 + s1 + n2 + ")" + s2  + n3 + ")" + s3 + n4
                    if min24 <= eval(expr) <= max24:
                        return True
    return False

def traverse_num(li):
    for i1 in range(4):
        for i2 in range(4):
            if i1 == i2: continue
            for i3 in range(4):
                if i3 == i1 or i3 == i2: continue
                for i4 in range(4):
                    if i4 == i1 or i4 == i2 or i4 == i3: continue
                    if compute24(li[i1], li[i2], li[i3], li[i4]):
                        return True
    return False

for line in sys.stdin.readlines():
    li = line.strip().split()
    print("true" if traverse_num(li) else "false")