go: add «260. Single Number III»

Signed-off-by: Matej Focko <me@mfocko.xyz>

go/single-number-iii.go

@@ -0,0 +1,33 @@
+package single_number_iii
+
+func singleNumber(nums []int) []int {
+	reduce := func() int {
+		xor := 0
+		for _, x := range nums {
+			xor ^= x
+		}
+		return xor
+	}
+	xor := reduce()
+
+	findMask := func() int {
+		mask := 1
+		for (xor & mask) == 0 {
+			mask <<= 1
+		}
+		return mask
+	}
+	mask := findMask()
+
+	a := 0
+	b := 0
+	for _, x := range nums {
+		if (x & mask) != 0 {
+			a ^= x
+		} else {
+			b ^= x
+		}
+	}
+
+	return []int{a, b}
+}