從後面往前讀，讀到f, g, h再往前找答案，因為python的str可以用split，且可以無痛轉成int

總之就是從後面開始讀，算好就把數值替換掉

x = input()
x = x.split(' ')
for i in range(len(x)-1, -1, -1):
    if x[i] == 'f':
        n = x[i+1] * 2 - 3
        del x[i]
        x[i] = n
    if x[i] == 'g':
        n = x[i+1] * 2 + x[i+2] - 7
        del x[i]
        del x[i]
        x[i] = n
    if x[i] == 'h':
        n = x[i+1] * 3 - x[i+2] * 2 + x[i+3]
        del x[i]
        del x[i]
        del x[i]
        x[i] = n
    else:
        x[i] = int(x[i])
print(x[0])

從後面往前讀，讀到f, g, h再往前找答案，因為python的str可以用split，且可以無痛轉成int

總之就是從後面開始讀，算好就把數值替換掉

def main():
    x = input().split(' ')
    for i in range(len(x)-1, -1, -1):
        if x[i] == 'f':
            x[i] = x[i+1] * 2 - 3
            del x[i+1:i+2]
            continue
        if x[i] == 'g':
            x[i] = x[i+1] * 2 + x[i+2] - 7
            del x[i+1:i+3]
            continue
        if x[i] == 'h':
            x[i] = x[i+1] * 3 - x[i+2] * 2 + x[i+3]
            del x[i+1:i+4]
            continue
        x[i] = int(x[i])
    print(x[0])
main()

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