c++ - Wrong answer while calculating the nth root of number in cpp -

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i calculating n'th root of positive integer using standard library method pow() .here snippet program :

double x,y; x=pow(64,(1.0/3)); int z; printf("x=%lf\n",x); z=(int)x; printf("%d\n",z);

but while finding cube root of 64. x printed 4.000000 while z 3. why ?

can suggest better algorithm , same ?

if print more digits on x, you'll see problem (i chose 30 randomly): 

double x ; x = pow(64, 1.0/3); printf("x=%.30lf\n",x);

output:

x=3.99999999...999600000000

so obvisouly, if cast x int became 3.

there not 'perfect' solution. if you're dealing integer, create own root function, if want able use float, you'need deal accuracy problem due floating point representation.

there maybe c libraries kind of problems.


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