added fast_integer_input.cpp (#696)

* added fast_integer_input.cpp

* fixed white spaces

* fixed white spaces

* fixed std::

* fixed std::

* \n

Co-authored-by: Christian Clauss <cclauss@me.com>

others/fast_interger_input.cpp

@@ -0,0 +1,36 @@
+// Read integers in the fastest way in c plus plus
+#include<iostream>
+void fastinput(int *number) {
+// variable to indicate sign of input integer
+    bool negative = false;
+    register int c;
+    *number = 0;
+
+    // extract current character from buffer
+    c = std::getchar();
+    if (c == '-') {
+        // number is negative
+        negative = true;
+
+        // extract the next character from the buffer
+        c = std::getchar();
+    }
+
+    // Keep on extracting characters if they are integers
+    // i.e ASCII Value lies from '0'(48) to '9' (57)
+    for (; (c > 47 && c < 58); c = std::getchar())
+        *number = *number *10 + c - 48;
+
+    // if scanned input has a negative sign, negate the
+    // value of the input number
+    if (negative)
+        *(number) *= -1;
+}
+
+// Function Call
+int main() {
+    int number;
+    fastinput(&number);
+    std::cout << number << "\n";
+    return 0;
+}