add solution for climbing-stairs

Author: Hyeri1ee

climbing-stairs/Hyeri1ee.java

@@ -0,0 +1,27 @@
+import java.util.*;
+
+class Solution {
+    public int climbStairs(int n) {
+        int[] steps = new int[n+1];
+        if (n == 1) return 1;
+        if (n == 2) return 2;
+        if (n == 3) return 3;
+        steps[1] = 1; steps[2] = 2;//2, 1+1
+        steps[3] = 3;
+        for(int i = 4;i < n+1; i++){
+            steps[i] = steps[i-1] + steps[i-2];
+        }
+        /*
+        steps[4] = 
+        1+1+1+1
+        1+2+1
+        2+2
+        2+1+1
+        1+1+2
+        */
+
+        return steps[n];
+        
+
+    }
+}