Question

1952. Three Divisors

中文文档

Description

Given an integer n, return true_ if _n_ has exactly three positive divisors. Otherwise, return _false.

An integer m is a divisor of n if there exists an integer k such that n = k * m.

 

Example 1:

Input: n = 2
Output: false
Explantion: 2 has only two divisors: 1 and 2.

Example 2:

Input: n = 4
Output: true
Explantion: 4 has three divisors: 1, 2, and 4.

 

Constraints:

• 1 <= n <= 104

Solutions

Solution 1

class Solution:
  def isThree(self, n: int) -> bool:
    return sum(n % i == 0 for i in range(2, n)) == 1

class Solution {
  public boolean isThree(int n) {
    int cnt = 0;
    for (int i = 2; i < n; i++) {
      if (n % i == 0) {
        ++cnt;
      }
    }
    return cnt == 1;
  }
}

class Solution {
public:
  bool isThree(int n) {
    int cnt = 0;
    for (int i = 2; i < n; ++i) {
      cnt += n % i == 0;
    }
    return cnt == 1;
  }
};

func isThree(n int) bool {
  cnt := 0
  for i := 2; i < n; i++ {
    if n%i == 0 {
      cnt++
    }
  }
  return cnt == 1
}

/**
 * @param {number} n
 * @return {boolean}
 */
var isThree = function (n) {
  let cnt = 0;
  for (let i = 2; i < n; ++i) {
    if (n % i == 0) {
      ++cnt;
    }
  }
  return cnt == 1;
};

Solution 2

class Solution:
  def isThree(self, n: int) -> bool:
    cnt = 0
    i = 1
    while i <= n // i:
      if n % i == 0:
        cnt += 1 if i == n // i else 2
      i += 1
    return cnt == 3

class Solution {
  public boolean isThree(int n) {
    int cnt = 0;
    for (int i = 1; i <= n / i; ++i) {
      if (n % i == 0) {
        cnt += n / i == i ? 1 : 2;
      }
    }
    return cnt == 3;
  }
}

class Solution {
public:
  bool isThree(int n) {
    int cnt = 0;
    for (int i = 1; i <= n / i; ++i) {
      if (n % i == 0) {
        cnt += n / i == i ? 1 : 2;
      }
    }
    return cnt == 3;
  }
};

func isThree(n int) bool {
  cnt := 0
  for i := 1; i <= n/i; i++ {
    if n%i == 0 {
      if n/i == i {
        cnt++
      } else {
        cnt += 2
      }
    }
  }
  return cnt == 3
}

/**
 * @param {number} n
 * @return {boolean}
 */
var isThree = function (n) {
  let cnt = 0;
  for (let i = 1; i <= n / i; ++i) {
    if (n % i == 0) {
      cnt += ~~(n / i) == i ? 1 : 2;
    }
  }
  return cnt == 3;
};