algorithm - Is there a way to loop over an integer array, keeping track of all unique elements WITHOUT allocating a new array? -


an array contains n elements, each element within range 1 <= k <= x x <= n. elements in no particular order, there many duplicate elements. wondering if there way iterate on array, stopping 1 of every integer 1-x has been seen, , doing without allocating additional array , without sorting original array.

edit: array guaranteed contain values 1-x. x parameter, not constant.

edit:

more generally, wondering if there known way of combining unique consecutive integers sum or product, such value of sum or product can tell whether or not 1 of integers part of it. multiplying unique primes together.

thanks

there trivial way, exceptionally inefficient. use 2 nested loops. untested pseudocode:

   lastindex = 0;    containsall = true;    ( i=1; <= x; ++ ) {        ( j=0; j < n; j++ ) {           if ( array(j) == ) {             if ( j > lastindex ) {                lastindex = j;             }             break;           }        }     }

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