lintcode2 尾部的零

这题就是在求阶乘后面的0，我第一次想的方法很简单，先乘出来然后在除10，肯定可以了。但是这个的时间复杂度超了

 

public class Solution {
    /*
     * @param n: An integer
     * @return: An integer, denote the number of trailing zeros in n!
     */
    public long trailingZeros(long n) {
        // write your code here, try to do it without arithmetic operators.
        int res =1;
        int tmp=0;
        for(int i =1;i<=n;i++){
            res = res*i;
        }
        while(res%10==0 )
        {
            tmp++;
            
        }
        return tmp;
    }
    
}

所以我们使用获取能被5整除的数字的方法来求值

public class Solution {
    /*
     * @param n: An integer
     * @return: An integer, denote the number of trailing zeros in n!
     */
    public long trailingZeros(long n) {
        // write your code here, try to do it without arithmetic operators.
        //int res =1;
        long q = n;
        long count = 0;
        while (q!=0){
            count +=q/5;
            q = q/5;
        }
        return count;
    }
    
}

其实是个数学问题，和你的编程能力没什么关系。。。