public?class??Test?{??
????public?static?void?f(int[]?a,?int?n)?{??
????????if?(n?==?a.length?-?1)?{??
????????????int?k?=?0;?//?把a里的數(shù)字組合為一個數(shù)字k??
????????????for(int?i=0;?i<a.length;?i++)?k?=?k*10?+?a[i];?
????????????int?m?=?(int)?(Math.sqrt(k)+0.5);??
????????????if?(m?*?m?==?k)?{??
????????????????System.out.println(k);??
????????????}??
????????????return;??
????????}??
????????//?全排列??
????????for?(int?i?=?n;?i?<?a.length;?i++)?{??
????????????int?t?=?a[n];??
????????????a[n]?=?a[i];??
????????????a[i]?=?t;??
??????????????
????????????f(a,?n+1);?
??????????????
????????????t?=?a[n];??
????????????a[n]?=?a[i];??
????????????a[i]?=?t;??
????????}??
????}??
????public?static?void?main(String[]?args)?{??
????????int[]?a?=?{?1,?9,?6?};??
????????f(a,?0);??
????}??
}