go: partition equal subset sum

Author: PoorlyDefinedBehaviour

golang/algorithms/others/partition_equal_subset_sum/main.go

@@ -0,0 +1,72 @@
+package main
+
+// Given an integer array nums, return true if
+// you can partition the array into two subsets such that the sum of the elements in both subsets is equal or false otherwise.
+//
+// Example 1:
+//
+// Input: nums = [1,5,11,5]
+// Output: true
+// Explanation: The array can be partitioned as [1, 5, 5] and [11].
+// Example 2:
+//
+// Input: nums = [1,2,3,5]
+// Output: false
+// Explanation: The array cannot be partitioned into equal sum subsets.
+//
+// Constraints:
+//
+// 1 <= nums.length <= 200
+// 1 <= nums[i] <= 100
+
+import (
+	"maps"
+)
+
+// time O(n)
+// space O(1)
+func sumSlice(nums []int) int {
+	sum := 0
+	for _, num := range nums {
+		sum += num
+	}
+	return sum
+}
+
+func canPartition(nums []int) bool {
+	// O(n)
+	sum := sumSlice(nums)
+	// If the sum is odd it is impossible to divide it in 2.
+	if sum&1 == 1 {
+		return false
+	}
+
+	half := sum / 2
+
+	seen := map[int]struct{}{
+		0: {},
+	}
+
+	// O(n)
+	for _, num := range nums {
+		newSeen := maps.Clone(seen)
+		// O(sum(nums))
+		for otherNum := range seen {
+			total := num + otherNum
+			if total == half {
+				return true
+			}
+			if total < half {
+				newSeen[total] = struct{}{}
+			}
+
+		}
+		seen = newSeen
+	}
+
+	return false
+}
+
+func main() {
+
+}