CODEWITHSUNDEEP
c++arrayswhile-loop
Odai Mohammed
Odai Mohammed

Reputation: 3

while loop keeps running

so this is my code snippet :

double numericalMethod::splineLinearInterpolation(){

int n, i=0;
double x[100], y[100], s[100],a;
cout << "Enter no. of sample points : \n";
cout << "\n";
cin  >> n;
cout << "\n";
cout << "Enter all values of x and corresponding functional value y :  \n";
cout << "\n";
cout << "x | y \n";
for (i=0; i<n; i++){
    cin >> x[i] >> y[i];
}
cout << "\n";
cout << "Enter the value of  x for which you would like to calculate the estimated value of y : \n ";
cout << "\n";
cin  >> a;
while (a<x[0] or a>x[n]){
    cout << "The selected value of x must belong to the domain [" << x[0] << "," << x[4] << "] \n" ;
    cout << "\n";
    cout << "Reenter the value of x please : ";
    cout << "\n";
    cin  >> a;
}
cout << "\n";

for (i=0; i<n-1; i++){
   s[i]=y[i] + ((y[i+1]-y[i])/(x[i+1]-x[i]))*(a-x[i]);
   if (a>=x[i] and a<=x[i+1])
       cout << "s[" << i << "] =" << s[i] << "   when " << x[i] << " <= x <=" << x[i+1] <<endl;

}
return 0;

}

x is an array

when ever my program enters the loop it never exits it

although when i switch x[0] and x[n] with constant numbers it runs perfectly

any ideas? and thanks

Upvotes: 0

Views: 119

Answers (1)

Carlos Mendoza
Carlos Mendoza

Reputation: 61

You are reading in this way:

for (i = 0; i < n; i++) {
  cin >> x[i] >> y[i];
}

Array x will have values in the positions: [0, N-1]

But in this while: 

while (a < x[0] or a > x[n] ){

Your trying to access position N of the array, which will be a random number if not initialized.

Upvotes: 3

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