Merge pull request #2992 from benmak11/combination-sum-iv

Update 0377-combination-sum-iv

Author: felivalencia3

java/0377-combination-sum-iv.java

@@ -1,5 +1,4 @@
-class Solution {
-  
+class Solution {  
   /*       Tabulation Method
       --------------------------
       T = Target, N = nums.length
@@ -48,4 +47,26 @@ private int helper(int[] nums, int t, HashMap<Integer, Integer> memo){
         memo.put(t, count);
         return count;        
     }
+  
+  /** 
+      Simple brute force, count num of combinations
+      using Map ds
+      Time complexity: O(n)
+      Space complexity: O(n)
+  */
+    public int combinationSum4(int[] nums, int target) {
+        Map<Integer, Integer> cache = new HashMap<>();
+
+        cache.put(0, 1);
+
+        for (int i = 1; i < target + 1; i++) {
+            cache.put(i, 0);
+            for (int n : nums) {
+                int temp = cache.containsKey(i - n) ? cache.get(i - n) : 0;
+                cache.put(i, cache.get(i) + temp);
+            }
+        }
+
+        return cache.get(target);
+    }
 }