feat(solutions): add climbing_stairs

Author: WindomZ

README.md

@@ -25,6 +25,7 @@
 
 | # | Problem | Solution | Difficulty | Single Repetition Duration | LeetCode Run Time |
 | ---: | :----- | :--------: | :----------: | ----------: | ----------: |
+|70|[Climbing Stairs][Solutions-70]|[WindomZ][Solutions-70-go]|Easy|[7.59 ns/op/9 test cases][Solutions-70-Test]|0 ms|
 |69|[Sqrt(x)][Solutions-69]|[WindomZ][Solutions-69-go]|Easy|[27.6 ns/op/8 test cases][Solutions-69-Test]|6 ms|
 |67|[Add Binary][Solutions-67]|[WindomZ][Solutions-67-Go]|Easy|[84.0 ns/op/5 test cases][Solutions-67-Test]|3 ms|
 |66|[Plus One][Solutions-66]|[WindomZ][Solutions-66-Go]|Easy|[29.8 ns/op/6 test cases][Solutions-66-Test]|3 ms|
@@ -123,6 +124,9 @@ Welcome to report bugs, suggest ideas and discuss on [issues page](https://githu
 ### Support
 If you like it then you can put a :star:Star on it.
 
+[Solutions-70]:https://leetcode.com/problems/climbing-stairs/
+[Solutions-70-go]:solutions/climbing_stairs/climbingstairs.go
+[Solutions-70-Test]:solutions/climbing_stairs/climbingstairs_test.go#L17
 [Solutions-69]:https://leetcode.com/problems/sqrtx/
 [Solutions-69-go]:solutions/sqrtx/sqrtx.go
 [Solutions-69-Test]:solutions/sqrtx/sqrtx_test.go#L23

solutions/climbing_stairs/README.md

@@ -0,0 +1,34 @@
+# 70. Climbing Stairs
+
+[Description](https://leetcode.com/problems/climbing-stairs/description/) | 
+[Discuss](https://leetcode.com/problems/climbing-stairs/discuss/) | 
+[Solution](https://leetcode.com/problems/climbing-stairs/solution/)
+
+## Description
+
+You are climbing a stair case. It takes _n_ steps to reach to the top.
+
+Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
+
+**Note:** Given _n_ will be a positive integer.
+
+**Example 1:**
+```
+Input: 2
+Output:  2
+Explanation:  There are two ways to climb to the top.
+
+1. 1 step + 1 step
+2. 2 steps
+```
+
+**Example 2:**
+```
+Input: 3
+Output:  3
+Explanation:  There are three ways to climb to the top.
+
+1. 1 step + 1 step + 1 step
+2. 1 step + 2 steps
+3. 2 steps + 1 step
+```

solutions/climbing_stairs/climbingstairs.go

@@ -0,0 +1,16 @@
+package climbingstairs
+
+func climbStairs(n int) int {
+	// can reach (i) step in one of the two ways:
+	// 1. taking a single step from (i-1) step.
+	// 2. taking a step of 2 from (i-2) step.
+	// so
+	// 'current' is (i-1) -> (i) step
+	// 'next' is (i) -> (i+1) step
+	// reach (i+1) step: (i) step + (i-1) step
+	current, next := 1, 1
+	for ; n > 0; n-- {
+		current, next = next, current+next
+	}
+	return current
+}

solutions/climbing_stairs/climbingstairs_test.go

@@ -0,0 +1,34 @@
+package climbingstairs
+
+import (
+	"testing"
+
+	"github.com/WindomZ/testify/assert"
+)
+
+func Test_climbStairs(t *testing.T) {
+	assert.Equal(t, 1, climbStairs(1))
+	assert.Equal(t, 2, climbStairs(2))
+	assert.Equal(t, 3, climbStairs(3))
+	assert.Equal(t, 5, climbStairs(4))
+	assert.Equal(t, 8, climbStairs(5))
+}
+
+func Benchmark_climbStairs(b *testing.B) {
+	b.StopTimer()
+	b.ReportAllocs()
+	b.StartTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			climbStairs(1)
+			climbStairs(2)
+			climbStairs(3)
+			climbStairs(4)
+			climbStairs(5)
+			climbStairs(6)
+			climbStairs(7)
+			climbStairs(8)
+			climbStairs(9)
+		}
+	})
+}