Random1000 Using Random5

update Mar 16,2018 23:45

Given a random generator random5(), the return value of random5() is 0 - 4 with equal probability. Use random5() to implement random1000();

Basic Idea:

和之前的题目 Random7 Using Random5 类似，只是这道题我们需要用循环逻辑来生成这个五进制数的每一位，直到其可以大于1000，这个数字是3124，则我们可以先生成 random3125(), 然后取前 3000 个数 [0,1,2...,2999], 然后 mod 1000 即可。

• Java Code:

  public class Solution {
    public int random1000() {
      // Write your solution here.
      // you can use RandomFive.random5() for generating
      // 0 - 4 with equal probability.
      while (true) {
        int rand = 0;
        for (int digit = 4; digit >= 0; --digit) {
          rand += RandomFive.random5() * Math.pow(5, digit);
        }
        if (rand < 3000) return rand % 1000;
      }
    }
  }