Right away, I can tell it’s not going to be easy. No square number ends with 2, 3, 7 or 8.
Assuming the number is square, the first digit can be found through successive approximation, the last digit is then mapped to 0→0, 1→1/9, 4→2/8, 5→5, 6→4/6, 9→3/7. To differentiate between the low/high number in ambiguous cases, one can estimate the difference from the bottom/top of the decade, compare to ⌷5² (can be calculated with an easy trick) or check for division by 3.
Right away, I can tell it’s not going to be easy. No square number ends with 2, 3, 7 or 8.
Assuming the number is square, the first digit can be found through successive approximation, the last digit is then mapped to 0→0, 1→1/9, 4→2/8, 5→5, 6→4/6, 9→3/7. To differentiate between the low/high number in ambiguous cases, one can estimate the difference from the bottom/top of the decade, compare to ⌷5² (can be calculated with an easy trick) or check for division by 3.
not a square of integer
Yeah, that’s what “square number” means.
thanks, first time I’m seeing this, not a native speaker