Create 70. Climbing Stairs.java

Author: cyzlcyzl

leetcode3/염혜정/70. Climbing Stairs.java

@@ -0,0 +1,14 @@
+// O(n)
+
+class Solution {
+    public int climbStairs(int n) {
+        int[] cnt = new int[n+1];
+        cnt[1] = 1;
+        if (n >= 2) cnt[2] = 2;
+
+        for (int i = 3; i<=n; i++) {
+            cnt[i] = cnt[i-1] + cnt[i-2];
+        }
+        return cnt[n];
+    }
+}