I am trying to use an array in an If statement

Question

I am trying to use an array in an if statement to determine whether the value of x is rare or not.

If I do it this way everything is common.

#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

int main(){
    int y[5] = {1,2,3,4,5};
    srand(time(0));
for(int z = 0; z <= 50; z++){
    int x = 1 + (rand()%6);
    cout << z;
    cout << " " <<x;
    if(y[5] == x){
        cout << ": Common" << endl;
    }else{
        cout << ": RARE" << endl;
    }
}

But if I do it this way everything is rare.

#include <iostream>
#include <cstdlib>
#include <ctime>

using namespace std;

int main(){
    int y[5] = {1,2,3,4,5};
    srand(time(0));
for(int z = 0; z <= 50; z++){
    int x = 1 + (rand()%6);
    cout << z;
    cout << " " <<x;
    if(y[5] == ++x){
        cout << ": Common" << endl;
    }else{
        cout << ": RARE" << endl;
    }
}

I am really stumped on what to do can someone please help me?

Indexes start at 0, so y[5] is already out of bounds of your 5-element array. — shree.pat18
– shree.pat18, Commented Aug 14, 2014 at 4:42

roelofs · Accepted Answer · 2014-08-14 04:43:43Z

1

You are also accessing the array in position 6 (out of bounds) in both cases. You are simply lucky that the first one works, but not the second one.

Change it to y[4] (array indexing starts at 0).

answered Aug 14, 2014 at 4:43

roelofs

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Comments

quantdev · Accepted Answer · 2014-08-14 04:41:55Z

1

Your program has undefined behavior. y[5] is accessing the array out of bounds.

Use y[N-1] to access the last element of an array of size N, so here you should use y[4]

answered Aug 14, 2014 at 4:41

quantdev

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