Update 递归相关.md

blogs/Algorithm/剑指 Offer/递归相关.md

@@ -24,3 +24,25 @@ class Solution {
 }
 ```
 
+#### [10- II. 青蛙跳台阶问题](https://leetcode-cn.com/problems/qing-wa-tiao-tai-jie-wen-ti-lcof/)
+
+```java
+class Solution {
+
+    public int numWays(int n) {
+        int result = 0;
+        int start = 1;
+        int end = 1;
+        if (n == 0 || n == 1) {
+            return 1;
+        }
+        for (int i = 2; i <= n; i++) {
+            result = (start + end) % 1000000007;
+            start = end;
+            end = result;
+        }
+        return result;
+    }
+}
+```
+