Missing number array code

Author: PabloAceG

MissingNumberArray.cpp

@@ -0,0 +1,18 @@
+#include <iostream>
+#include <numeric>
+#include <vector>
+
+int sumOfElements(const std::vector<int> series) {
+    return std::accumulate(series.begin(), series.end(), 0);
+}
+
+int sumOfElements(const int n) {
+    return (n * (1 + n)) / 2;
+}
+
+int find_missing(const std::vector<int>& input) {
+    int expectedSum = sumOfElements(input);
+    int realSum = sumOfElements(input.size() + 1);
+
+    return realSum - expectedSum;
+}