objective c - Check if any values have changed a certain amount -


does know efficient ways check if set of integers contains integer has changed amount.

for example have:

int1 = 10; int2 = 20; int3 = 30;

and want know if of these 3 integers change 30

now if int1 becomes 40 call should triggered. @ first thought of doing this.

if (abs((int1+int2+int3)-(newint1+newint2+newint3)) >= 30) {

but many problems can arise this...

  • false triggers (e.g. each new int value increases 10, making net change greater 30 not individual int greater 30)
  • untriggered reactions (e.g. 1 of new integer values has increased 50 should called new integer value decreased 50 (again, should called) net change 0 because -50+50=0)

does have efficient way of doing this? (yes, know check each value individually or statements...)

so far best stab @ 

if ((((abs(int1-newint1))>=30)+((abs(int2-newint2))>=30)+((abs(int3-newint3))>=30))>0) {

but that's basically same using or statement (probably takes little longer or statment.

i don't think can faster that, , unless you're dealing hundreds of millions of integers, should not introduce significant performance penalty.

however, might want "clever". if somehow "checksum" 2 sums? example, multiply old , new numbers nth prime, check if difference of new , old sum divided indexth prime amount want.

int sum(int arr[], size_t n) {     int n = 0;     (int = 0; < n; i++)         n += primes[i] * arr[i];      return n; }  int primes[3] = { 2, 3, 5 }; // or more int olds[3] = { 10, 20, 30 }; int news[3] = { 40, 20, 30 };  int nth = 0; // check first int change_expected = 30; int oldsum = sum(olds, 3); int newsum = sum(news, 3); if ((newsum - oldsum) / primes[nth] == change_expected) {     // 1st value changed expected }

note take way more time , cpu cycles naive approach.


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