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[Algorithm] FrogJmp


Question

A small frog wants to get to the other side of the road. The frog is currently located at position X and wants to get to a position greater than or equal to Y. The small frog always jumps a fixed distance, D.

Count the minimal number of jumps that the small frog must perform to reach its target.

Write a function:

function solution(X, Y, D);

that, given three integers X, Y and D, returns the minimal number of jumps from position X to a position equal to or greater than Y.

For example, given:

  X = 10
  Y = 85
  D = 30

the function should return 3, because the frog will be positioned as follows:

  • after the first jump, at position 10 + 30 = 40
  • after the second jump, at position 10 + 30 + 30 = 70
  • after the third jump, at position 10 + 30 + 30 + 30 = 100

Write an efficient algorithm for the following assumptions:

  • X, Y and D are integers within the range [1..1,000,000,000];
  • X ≤ Y.

Solution (TypeScript)

function solution(x: number, y: number, d: number) {
  if (x === y) {
    return 0;
  }
  return Math.ceil((y - x) / d);
}

Author: Codility, Lesson 3

20200106 Charyum.Park