202. Happy number

#include <stdbool.h>

static int next(int n) {
  int sum = 0;
  while (n > 0) {
    int d = n % 10;
    sum += d * d;
    n /= 10;
  }
  return sum;
}

bool isHappy(int n) {
  int slow = n, fast = next(n);
  while (fast != 1 && slow != fast) {
    slow = next(slow);
    fast = next(next(fast));
  }
  return fast == 1;
}

class Solution {
  int next(int n) {
    int sum = 0;
    while (n > 0) {
      int d = n % 10;
      sum += d * d;
      n /= 10;
    }
    return sum;
  }

public:
  bool isHappy(int n) {
    int slow = n, fast = next(n);
    while (fast != 1 && slow != fast) {
      slow = next(slow);
      fast = next(next(fast));
    }
    return fast == 1;
  }
};

package mathgeometry

func next(n int) int {
    sum := 0
    for n > 0 {
        d := n % 10
        sum += d * d
        n /= 10
    }
    return sum
}

func isHappy(n int) bool {
    slow, fast := n, next(n)
    for fast != 1 && slow != fast {
        slow = next(slow)
        fast = next(next(fast))
    }
    return fast == 1
}

class Solution {
    private int next(int n) {
        int sum = 0;
        while (n > 0) {
            int d = n % 10;
            sum += d * d;
            n /= 10;
        }
        return sum;
    }

    public boolean isHappy(int n) {
        int slow = n, fast = next(n);
        while (fast != 1 && slow != fast) {
            slow = next(slow);
            fast = next(next(fast));
        }
        return fast == 1;
    }
}

const next = (n) => {
  let sum = 0;
  while (n > 0) {
    const d = n % 10;
    sum += d * d;
    n = Math.floor(n / 10);
  }
  return sum;
};

/**
 * @param {number} n
 * @return {boolean}
 */
var isHappy = function (n) {
  let slow = n, fast = next(n);
  while (fast !== 1 && slow !== fast) {
    slow = next(slow);
    fast = next(next(fast));
  }
  return fast === 1;
};

class Solution:
    def next(self, n: int) -> int:
        total = 0
        while n > 0:
            n, d = divmod(n, 10)
            total += d * d
        return total

    def isHappy(self, n: int) -> bool:
        slow, fast = n, self.next(n)
        while fast != 1 and slow != fast:
            slow = self.next(slow)
            fast = self.next(self.next(fast))
        return fast == 1

impl Solution {
    fn next(mut n: i32) -> i32 {
        let mut sum = 0;
        while n > 0 {
            let d = n % 10;
            sum += d * d;
            n /= 10;
        }
        sum
    }

    pub fn is_happy(n: i32) -> bool {
        let (mut slow, mut fast) = (n, Self::next(n));
        while fast != 1 && slow != fast {
            slow = Self::next(slow);
            fast = Self::next(Self::next(fast));
        }
        fast == 1
    }
}