Solved the Max Array Sum.

Author: jonasraoni

README.md

@@ -67,6 +67,7 @@ Note: Few codes were solved in C# (I've written them a long time ago), I'll conv
 
 - [Count Triplets](challenges/countTriplets.js)
 - [Frequency Queries](challenges/freqQuery.js)
+- [Max Array Sum](challenges/maxSubsetSum.js)
 - [Minimum Swaps 2](challenges/minimumSwaps.js)
 - [Special String Again](challenges/substrCount.js)
 

challenges/maxSubsetSum.js

@@ -0,0 +1,31 @@
+//+ Jonas Raoni Soares Silva
+//@ http://raoni.org
+
+function maxSubsetSum(arr) {
+	let sum = 0;
+	// Head is the current best index
+	// As we go walking through the array, we're keeping the sums saved, so it becomes easier to switch the path
+	for (let previous = -1, head = -2, i = -1, l = arr.length; ++i < l; ) {
+		const v = arr[i];
+		// Skip non-positive numbers
+		if (v < 1)
+			continue;
+		// If it's an adjacent item, add to the sum (also replace the number by the sum at this position)
+		if (head + 1 != i)
+			arr[i] = sum += v;
+		else {
+			// Does the previous adjacent item offer a bigger sum?
+			const newSum = arr[i] += previous > -1 ? arr[previous] : 0;
+			if (newSum <= sum) {
+				// If not, just mark it as a valid adjacent item
+				previous = i;
+				continue;
+			}
+			sum = newSum;
+		}
+		// If we ended up here, the sum was updated, so we need to update our indexes
+		previous = head;
+		head = i;
+	}
+	return sum;
+}