Why I can not see output in cycle (C simple code)?-CodePudding

I would like to edit numbers in p2 according to the code in for cycle. But If I try to write out actual number in p2, I don´t see anything in output. What could I change to see it?

#include <iostream>

using namespace std;

int main()
{
        
    int p1[10]={-5,-8,0,5,0,-8,-11,-2,1,-7};
    int p2[10]={0,0,0,0,0,0,0,0,0,0};
    
    for(int i; i >0; i  ){
        p2[i] = p2[i] - p1[i];
        cout << p2[i];
    }
    
}

CodePudding user response：

As pointed out by Ilya, you need to change the condition in the for loop. Right now, at the beginning of the for loop, i = 0, so the for loop never starts. Change it to the following:

#include <iostream>

using namespace std;

int main()
{
        
    int p1[10]={-5,-8,0,5,0,-8,-11,-2,1,-7};
    int p2[10]={0,0,0,0,0,0,0,0,0,0};
    
    for(int i = 0; i < 10; i  ){
        p2[i] = p2[i] - p1[i];
        cout << p2[i];
    }
    
}

CodePudding user response：

Since you did not initialize the value of i it takes the random value that is stored in its location.

So just make i 0 and loop it through until 10.

    #include <iostream>

using namespace std;

int main()
{
        
    int p1[10]={-5,-8,0,5,0,-8,-11,-2,1,-7};
    int p2[10]={0,0,0,0,0,0,0,0,0,0};
    
    for(int i = 0; i < 10; i  ){
        p2[i] = p2[i] - p1[i];
        cout << p2[i];
    }
    return 0;
}

CodePudding user response：

Because you didn't initialize the i variable, it takes a random number of type int, causing the loop to misbehave. You need to make i=0 for it to work correctly.

int p1[10]={-5,-8,0,5,0,-8,-11,-2,1,-7};
int p2[10]={0,0,0,0,0,0,0,0,0,0};

for(int i=0; i < sizeof(p1)/sizeof(p1[0]); i  ){
    p2[i] = p2[i] - p1[i];
    cout << p2[i];
}

sizeof(p1)/sizeof(p1[0]) is count of array elements.