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请教。我得解法是O(n)的。但是不知道哪儿错了。a=(bc-1)/(b+c) 令k=b+c 则b=k-c 所以a=((k-c)c-1)/k 化简为c*c+kc+(ak+1)=0; c=(-k+sqrt(k*k-4(a*k+1))/2 相应的b=(-k-sqrt(k*k-4(a*k+1))/2 因此我直接对k进行循环,依次k=k+1直到sqrt(k*k-4(a*k+1))为整数。。 但是不知道。为什么就WA了。。。。 #include <iostream.h> #include <math.h> int main() { unsigned long a,k; cin>>a; k=4*a; //因为sqrt中的k*k-4(a*k+1)必须为正。 long double t; t=sqrtl((unsigned long)(k*k-4*(a*k+1))); while (!(abs(t-(unsigned long)(t))<0.00000001)) { k++; t=sqrtl((unsigned long)(k*k-4*(a*k+1))); } cout<<k<<endl; return 0; } Followed by:
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