solve climbing stairs

Author: samcho0608

climbing-stairs/samcho0608.java

@@ -0,0 +1,21 @@
+class Solution {
+    // Problem:
+    // * can take 1 or 2 steps
+    // * return: how many distinct ways to climb to the top(n)
+    // Solution:
+    // * Time Complexity: O(N)
+    //   * due to memoization(DP)
+    // * Space Complexity: O(N)
+    public int climbStairs(int n) {
+        // memo[i] = distinct steps to reach ith step
+        int[] memo = new int[n + 1];
+        memo[0] = 1;
+        memo[1] = 1;
+
+        for(int i = 2; i < n+1; i++) {
+            memo[i] = memo[i-1] + memo[i-2];
+        }
+
+        return memo[n];
+    }
+}