Finding the missing number in an integer array (question from geeksforgeeks.com)

Question

1.00/5 (3 votes)

See more:

I am given an array of integers where the integers are sorted in an increasing order and the difference between adjacent elements is one except for a particular pair of integers where the difference is two. I have to locate the missing integer. I have written the code and so far, I cannot see any problem with it but the required output is not being produced. I would like yourhelp in understanding the mistake in my code.

Example: 11 12 13 15
The missing number is 14

Example: 3 5 6 7
The missing integer is 4

What I have tried:

This is my code. I am gettin the output as 12 for the array values below.

<pre>// ConsoleApplication2.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"

#include <iso646.h>
#include <vector>
#include <string>
#include<iostream>
#include <algorithm>


using namespace std;

int FindMissingNumber(vector<int>& nums)
{
	int result = 0;

	//sort(nums.begin(), nums.end());

	for (int i = 0; i < nums.size(); i++)
	{
		for (int j = i + 1; j < nums.size() - 1; j++)
		{
			if (nums[j] - nums[i] == 2)
			{				
				result = (nums[i] + 1);
			}
		}
	}

	return result;
}

int main() {
 
	vector<int> nums = { 10, 11, 12, 13, 15 };

		cout << FindMissingNumber(nums) << endl;	

	system("pause");
	return 0;
}

Posted 23-May-17 16:13pm

Member 13192781

Updated 23-May-17 21:17pm

v3

Add a Solution

Comments

Peter_in_2780 23-May-17 22:55pm

Big hint. You only need one loop.

2 solutions

Solution 1

Quote:
I have written the code and so far, I cannot see any problem with it but the required output is not being produced.

As already told you, use the debugger to see what your code is doing.
Think about what you have to do to solve the problem by hand, and look at what your code is doing with debugger.

When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute, it is an incredible learning tool.

Debugger - Wikipedia, the free encyclopedia[^]
Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.

Posted 23-May-17 16:58pm

Patrice T

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

CPallini · Accepted Answer · 2017-05-23T21:17:00

The logic of your FindMissingNumber function is flawed. Try:

C++

#include <vector>
#include <string>
#include <iostream>


using namespace std;

bool FindMissingNumber(const vector<int>& nums, int & result)
{
  for (size_t i = 0; i < nums.size()-1; i++)
  {
    if ( nums[i] != nums[i+1]-1)
    {
      result = (nums[i]+1);
      return true;
    }
  }
  return false;
}

int main()
{
  vector<int> nums = { 10, 11, 12, 13, 15 };

  int result;
  if ( FindMissingNumber( nums, result) )
    cout << "missing number is " << result << endl;
  else
    cout << "there is no missing number" << endl;
  return 0;
}