[Algorithm] 2. Trailing Zeros

Description

Write an algorithm which computes the number of trailing zeros in n factorial.

Example

11! = 39916800, so the out should be 2

Challenge

O(log N) time

Answer

     /*

      * @param n: A long integer

      * @return: An integer, denote the number of trailing zeros in n!

      */

     long long trailingZeros(long long n) {

         // write your code here, try to do it without arithmetic operators.

         if(n<){

             return ;

         }

         else{

             return n/ + trailingZeros(n/);

         }

     }

Tips

This solution is implemented by a recursive method, we can also use a loop method to solve this problem.

     /*

      * @param n: A long integer

      * @return: An integer, denote the number of trailing zeros in n!

      */

     long long trailingZeros(long long n) {

         // write your code here, try to do it without arithmetic operators.

         long long result = ;

         while ( n > )

         {

             result += n/;

             n /= ;

         }

         return result;

     }

巴特西