Merge pull request #242 from 0xff-dev/master

Add solution and test-cases for problem 172

Author: 6boris

leetcode/101-200/0172.Factorial-Trailing-Zeroes/README.md

@@ -0,0 +1,34 @@
+# [172. Factorial Trailing Zeroes][title]
+
+## Description
+Given an integer `n`, return the number of trailing zeroes in `n!`.
+
+Note that `n! = n * (n - 1) * (n - 2) * ... * 3 * 2 * 1`.
+
+**Example 1:** 
+```
+Input: n = 3
+Output: 0
+Explanation: 3! = 6, no trailing zero.
+```
+
+**Example 2:**
+```
+Input: n = 5
+Output: 1
+Explanation: 5! = 120, one trailing zero.
+```
+
+**Example 3:**
+```
+Input: n = 0
+Output: 0
+```
+
+
+## 结语
+
+如果你同我一样热爱数据结构、算法、LeetCode，可以关注我 GitHub 上的 LeetCode 题解：[awesome-golang-algorithm][me]
+
+[title]: https://leetcode.com/problems/factorial-trailing-zeroes/
+[me]: https://github.com/kylesliu/awesome-golang-algorithm

leetcode/101-200/0172.Factorial-Trailing-Zeroes/Solution.go

@@ -1,5 +1,23 @@
 package Solution
 
-func Solution(x bool) bool {
-return x
+func Solution(n int) int {
+count := 0
+countOfFive := make(map[int]int)
+for step := 5; step <= n; step += 5 {
+countOfFive[step] = 1
+if c, ok := countOfFive[step/5]; ok {
+countOfFive[step] += c
+}
+count += countOfFive[step]
+}
+return count
+}
+
+func Solution2(n int) int {
+res := 0
+for n > 0 {
+res += n / 5
+n /= 5
+}
+return res
 }

leetcode/101-200/0172.Factorial-Trailing-Zeroes/Solution_test.go

@@ -10,12 +10,13 @@ func TestSolution(t *testing.T) {
 //	测试用例
 cases := []struct {
 name string
-inputs bool
-expect bool
+inputs int
+expect int
 }{
-{"TestCase", true, true},
-{"TestCase", true, true},
-{"TestCase", false, false},
+{"TestCase1", 3, 0},
+{"TestCase2", 5, 1},
+{"TestCase3", 0, 0},
+{"TestCase4", 150, 37},
 }
 
 //	开始测试
@@ -26,6 +27,12 @@ func TestSolution(t *testing.T) {
 t.Fatalf("expected: %v, but got: %v, with inputs: %v",
 c.expect, got, c.inputs)
 }
+
+got = Solution2(c.inputs)
+if !reflect.DeepEqual(got, c.expect) {
+t.Fatalf("expected: %v, but got: %v, with inputs: %v",
+c.expect, got, c.inputs)
+}
 })
 }
 }