Python版本

import sys

def check(passwd):
    status = True
    if len(passwd) >= 8:
        flags = [False] * 4
        for c in passwd:
            if '0' <= c <= '9':
                flags[0] = True
            elif 'a' <= c <= 'z':
                flags[1] = True
            elif 'A' <= c <= 'Z':
                flags[2] = True
            elif c != ' ' and c != '\n':
                flags[3] = True
            else:
                status = False
        status = status and flags.count(True) >= 3
        for i in range(len(passwd)-2):
            sub = passwd[i:i+3]
            if sub in passwd[i+3:]:
                status = status and False
    else:
        status = False

    if status:
        print("OK")
    else:
        print("NG")
        

for line in sys.stdin:
    check(line.strip())