climbing stairs

Author: eunhwa99

climbing-stairs/eunhwa99.java

@@ -0,0 +1,17 @@
+// n=2 (1,1), (2) -> 2 가지
+// n=3 (n=2, 1), (n=1, 2) -> 2 + 1 = 3가지
+// n=4 (n=3, 1), (n=2, 2) -> 3 + 2 = 5가지
+// n=5 (n=4, 1) , (n=3, 2)
+// n=k (n=k-1, 1), (n=k-2, 2)
+
+class Solution {
+    public int climbStairs(int n) {
+        int[] cntArray = new int[n + 1];
+        cntArray[0] = 1;
+        cntArray[1] = 1;
+        for (int i = 2; i <= n; ++i) { // 시간 복잡도: O(n)
+            cntArray[i] = cntArray[i - 1] + cntArray[i - 2];
+        }
+        return cntArray[n];
+    }
+}