Find an array index before and after a certain value

[kraigballa]

Alright, just like the title says I am trying to find the index of an array's value that is before and after a users chosen value. I know this sounds confusing..so let me break it down.

Let's say I have an array {1,3,5,9,13}
The user inputs 6 as their value.
I am trying to figure out how to find the index of 5 and 9, which are the values directly below and above 6. I know from looking at this array that the indexes are 2 and 3, but I can't figure out how to code something like this. Any ideas?

[ceruleus]

start with

int main( )
{

   return 0;
}

and see how far you can get, then come back and post your code and point out what's troubling you and people will give you some feedback!

[kraigballa]

Here you go. It's not like I haven't done anything!! The bolded area is where I am tied up at. I want to find the index of the values directly below and after the "angle" which is the user input.

if(angle >= left[0] && angle <= left[lpos-1]){
            for(int i=0; i < lpos; i++){
                if(angle == left[i]){ // Checking to see if value user entered is in data set
                    cout << "Coefficient of lift is " << right[i] << endl;
                    equals = true;
                }
                else if(i == (lpos-1) &&  equals == false){
                    if(left[i] < angle){
                        lowerAngle = i;
                    }
                    if(left[i] > angle && (lowerAngle + 1) == i){
                        higherAngle = i;
                    }
                }
                
                // Calculating Coefficient if not a value in data set
                coeff = left[higherAngle] + left[lowerAngle];
                cout << "Coefficient of lift is " << coeff << endl;
            }
        }else{
            cout << "The angle you entered is not within the bounds of the data set." << endl;
        }

[ceruleus]

the second if statement uses lowerAngle + 1, are you 100% sure lowerAngle has been initialized? In other words when you declare it does it look like

int lowerAngle;

or

int lowerAngle = 0;

Just a thought...