[Solved] Generating random number between 4 ints [closed]

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If those ranges are inclusive, you have (r1b-r1a+1)+(r2b-r2a+1) numbers to choose from. Use rand (or a better random number library) to pick a non-negative integer up to (r1b-r1a+1)+(r2b-r2a+1) (exclusive), then map that result back onto the ranges.

int pick = rand() % ((r1b-r1a+1)+(r2b-r2a+1));
pick += ( pick < (r1b-r1a+1) ) ? r1a : r2a;

Assumptions:

  • r1b >= r1a.
  • r2b >= r2a.

Supported:

  • Range 1 doesn’t have to be before range 2.
  • Overlapping ranges.
  • Negative range endpoints.

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solved Generating random number between 4 ints [closed]