Largest int from concatenated ints: Difference between revisions
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The sorting of the text array was to be by the notorious BubbleSort, taking advantage of the fact that each pass delivers the maximum value of the unsorted portion to its final position: the output could thereby be produced as the sort worked. Rather than mess about with early termination (no element being swapped) or attention to the bounds within which swapping took place, attention concentrated upon the comparison. Because of the left-alignment of the texts, a simple comparison seemed sufficient until I thought of unequal text lengths and then the following example. Suppose there are two numbers, 5, and one of 54, 55, or 56 as the other. Via normal comparisons, the 5 would always be first (because short texts are considered expanded with trailing spaces when compared against longer texts, and a space precedes every digit) however the biggest ordering is 5 54 for the first case but 56 5 for the last. This possibility is not exemplified in the specified examples. So, a more complex comparison is required. One could of course write a suitable function and consider the issue there but instead the comparison forms the compound text in the same manner as the result will be, in the two ways AB and BA, and looks to see which yields the bigger sequence. This need only be done for unequal length text pairs.
The source is F77 style, except for the declaration of XLAT(N), the use of <N> in the FORMAT statements instead of some large constant or similar, and the ability to declare an array via constants as in <code>(/"5","54"/)</code> rather than mess about declaring arrays and initialising them separately. The <code>I0</code> format code to convert a number (an actual number) into a digit string aligned leftwards in a CHARACTER variable of sufficient size is also a F90 introduction, though the B6700 compiler allowed a code <code>J</code> instead. This last is to demonstrate usage of actual numbers for those unpersuaded by the argument for ambiguity that allows for texts. If the <code>I0</code> format code is unavailable then <code>I9</code> (or some suitable size) could be used, followed by <code>text = ADJUSTL(text)</code>, except that this became an intrinsic function only in F90, so perhaps you will have to write a simple alignment routine. <lang Fortran> SUBROUTINE SWAP(A,B) !Why can't the compiler supply these!
INTEGER A,B,T
T = B
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