172.阶乘后的零 方法: class Solution { public int trailingZeroes(int n) { int ans = 0; for(int i = 5;i<=n;i+=5){ for(int x = i; x % 5==0; x/=5){ ++ans; } } return ans; } } 进一步优化: class Solution { public int trailingZeroes(int n) { int ans = 0; while (n != 0) { n /= 5; ans += n; } return ans; } }