可以人工枚举一下。
一共77个组合:
127,128,129,136,137,138,139,145,146,147,148,149,156,157,158,159,167,168,169,178,179,189,235,236,237,238,239,245,246,247,248,249,256,257,258,259,267,268,269,278,279,289,345,346,347,348,349,356,357,358,359,367,368,369,378,379,389,456,457,458,459,467,468,469,478,479,489,567,568,569,578,579,589,678,679,689,789,
total = 77
如果考虑排列顺序,三个不同数字的排列方案是 3!=6个。一共有 77*6=462个。
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编程枚举可以避免遗漏,附fortran代码: