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https://leetcode.com/problems/factorial-trailing-zeroes/

Explanation: ref.1 ref.2

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class Solution {
    public int trailingZeroes(int n) {
        return n==0?0:n/5+trailingZeroes(n/5);
    }
}
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/* factorial -> overflow
class Solution {
    public int trailingZeroes(int n) {
        String facNum=String.valueOf(fac((long)n));
        int cnt=0;
        for(int i=facNum.length()-1;i>=0;i--){
            if(facNum.charAt(i)=='0') cnt++;
            if(facNum.charAt(i)!='0') break;
        }
        return cnt;
    }
    public long fac(long n){
        if(n<=1) return 1;
        return n*fac(n-1);
    }
}*/
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