Poj1401 calculates the number of zeros at the end of the N factorial.

The question is quite scary. There will be more than 0 in 2*5, and more than 0 in 10. There will be more than two 0 in 25*4. This will be messy .... the conclusion is that N can be used! To make a qualitative factor decomposition, there must be a 5 ^ x item in it. The goal is to evaluate the value of X. That is to say, the number of five is 0. Then I started to traverse from 1 to n and started to use 5 Except, and then timed out. Later, I thought about how to simply remove 5, 5 ^ 2, and 5 ^ 3,CodeUltra short .....

# Include <stdio. h> int Cal (INT num) {int sum = 0; int I; for (I = 5; I <= num; I * = 5) {sum + = (Num/I);} return sum;} int main (void) {int t; int num; scanf ("% d", & T ); while (t --) {scanf ("% d", & num); printf ("% d \ n", Cal (Num);} return 0 ;}