Create code.js

02. Algorithms/09. Dynamic Programming/001. Target Sum/code.js

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+/** Recursion, memoization
+ * https://leetcode.com/problems/target-sum/
+ * 
+ * Time O(m*n) where n = nums.length and m = target;
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number}
+ */
+var findTargetSumWays = function(nums, target) {
+
+    const cache = new Map();
+
+    function dfs(i, total) {
+        const key = i + "-" + total;
+        if(cache.has(key)) return cache.get(key);
+
+        if(i === nums.length) {
+            if(total === target) return 1;
+            return 0;
+        }
+
+        const result = (dfs(i + 1, total + nums[i]) + dfs(i + 1, total - nums[i])); 
+        cache.set(key, result);
+        return cache.get(key);
+        // return cache[i+"-"+total];
+    }
+
+    return dfs(0,0);
+};