算法-丑数(中等)

/**
 * @param n: An integer
 * @return: the nth prime number as description.
 */
const nthUglyNumber = function(n) {
  // write your code here
};

// [1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24]
const nthUglyNumber = function(n) {
  let arr = [1];
  let min,
    nex2,
    nex3,
    nex5,
    i2 = i3 = i5 = 0;
  for (let i = 1; i < n; i++) {
    // 除了第一个数，每个数都是2、3、5的倍数，把它们的倍数找出来，数字较小添加进去
    nex2 = arr[i2] * 2;
    nex3 = arr[i3] * 3;
    nex5 = arr[i5] * 5;
    min = Math.min(nex2, nex3, nex5);
    // 增加他们的倍数 为下次计算做准备
    if (min === nex2) i2++;
    if (min == nex3) i3++;
    if (min == nex5) i5++;
    arr.push(min);
  }
  return arr[arr.length - 1];
  // return arr
};
console.log('输出', nthUglyNumber(9), nthUglyNumber(15));