Climbing Stairs.

leetcoders · May 8, 2013 · a2a19da · a2a19da
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diff --git a/ClimbingStairs.h b/ClimbingStairs.h
@@ -0,0 +1,27 @@
+/*
+ Author:     Annie Kim, anniekim.pku@gmail.com
+ Date:       May 8, 2013
+ Problem:    Climbing Stairs
+ Difficulty: Easy
+ Source:     http://leetcode.com/onlinejudge#question_70
+ Notes:
+ 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?
+
+ Solution: Clime one step from last stair or clime 2 steps from the last last stair.
+ */
+
+class Solution {
+public:
+    int climbStairs(int n) {
+        int last = 1;
+        int lastlast = 1;
+        for (int i = 2; i <= n; i++)
+        {
+            int step = last + lastlast;
+            lastlast = last;
+            last = step;
+        }
+        return last;
+    }
+};
diff --git a/README.md b/README.md
@@ -76,6 +76,7 @@ All the codes are tested using online-judge.
 * Longest Palindromic Substring
 * Next Permutation
 * Longest Valid Parentheses
+* Climbing Stairs
 
 ### Linked List
 * Add Two Numbers