Binary Search - Output is not displaying after code compiles and runs - c++

Question

I'm just now learning about binary search in class and the code below is simply an example because I'm trying to understand it better. So with that said this code is compiling but not displaying any output and because of my lack of knowledge of Binary search I do not know why there isn't any output. Can someone please point in the direction of really well written tutorials, please? Or help indicate what is wrong with the code.
#include "stdafx.h"
#include <iostream>
#include <iomanip>
#include <conio.h>
#include <vector>
#include <algorithm>
using namespace std;
int SIZE = 10;
int main()
{
int thisArray[] = { 99,86,44,55,78,63,0,32,11 };
int num = 0;
int n = 0;
int first;
int last;
int middle;
first = 0;
last = n - 1;
middle = (first + last) / 2;
cout << "Enter the total number of elements\n";
cin >> n;
cout << "Entered " << n << "number.\n";
for (int i = 0; i < n; i++) {
cin >> thisArray[i];
}
cout << "Enter a number to find.\n";
cin >> num;
while (first <= last) {
if (thisArray[middle] < num) {
first = middle + 1;
}
else if (thisArray[middle] == num ) {
cout << num << " found at location " << middle + 1 << "\n";
break;
}
else {
last = middle - 1;
}
middle = (first + last) / 2;
}
return 0;
}
edit:
#include "stdafx.h"
#include <iostream>
#include <iomanip>
#include <conio.h>
#include <vector>
#include <algorithm>
using namespace std;
int SIZE = 10;
int main()
{
//this is my binary search
int thisArray[10] = { 0,11,32,44,55,63,78,86,99 };
int i = 0; //index of the array
int n = 0; //variable of number that will be looked for
int first = 0;
int last = SIZE - 1;
int middle;
int pos = -1;
bool found = false;
int count = 0;
while (found) {
cout << "Enter a number to look for.\n";
cin >> n;
while (first <= last) {
middle = first + last / 2;
if (thisArray[middle] == n) {
pos = middle;
cout << "item found at " << middle + 1 << "\n";
exit(0);
}
else if (thisArray[middle] > n) {
last = middle - 1;
}
else {
first = middle + 1;
}//endif
}//end while
}//end big while
//if()
return 0;
}
I got it. Thanks for the help everyone!

Answer 1

It's not outputting anything because first == 0 and last == -1. Hence first <= last is never true and the loop body is never executed.

Answer 2

you know what ? how can you even be using binary search if the array is not sorted properly to use binary search property ... and please , stop answering question like Jack meagher style, I hate answer that isn't directly addressing the problem , its kinda restating the question ...

Answer 3

Simple
Change last = n - 1; to last = SIZE - 1;
Or calculate last = n - 1; after u have accepted the value of n
Also the array needs to be sorted!

Answer 4

Figured it out. Now though the code was an example that I had found the for loop was not working correctly for me, so I got rid of it. And for iteration I implemented a do-while loop. However, the code the works now.
#include "stdafx.h"
#include <iostream>
#include <iomanip>
#include <conio.h>
#include <vector>
#include <algorithm>
using namespace std;
int SIZE = 10;
int main()
{
//this is my binary search
int thisArray[10] = { 0,11,32,44,55,63,78,86,99 };
int i = 0; //index of the array
int n = 0; //variable of number that will be looked for
int first = 0;
int last = SIZE - 1;
int middle;
int pos = -1;
bool found = false;
int count = 0;
do {
cout << "Enter a number to look for.\n";
cin >> n;
while (first <= last) {
middle = first + last / 2;
if (thisArray[middle] == n) {
pos = middle;
cout << "item found at " << middle + 1;
exit(0);
}
else if (thisArray[middle] > n) {
last = middle - 1;
}
else {
first = middle + 1;
}//endif
}//end while
} while (found = true);
return 0;
}