Add new Sol

Author: coderjojo

CodeSignal/InteviewQuestions/missingNumber.cpp

@@ -0,0 +1,10 @@
+int missingNumber(std::vector<int> arr) {
+    int sum=0,rsum=0, n = arr.size();
+    rsum = (n*(n+1))/2;
+
+    for(int i = 0; i < n; i++){
+        sum+=arr[i];
+    }
+
+    return abs(rsum-sum);
+}