Strange behaviour of pointers in C++ - c++

Question

#include <cstdlib>
#include <iostream>
#include <Math.h>
#include <algorithm>
#include <string>
#include <iterator>
#include <iostream>
#include <vector> // std::vector
using namespace std;
int stepCount, i, x, y, z, j, k, array1Size, array2Size, tester, checker;
int numstring[10] = { 0,1,2,3,4,5,6,7,8,9 };
int numstringTest[10] = { 0,1,2,3,4,5,6,7,7,9 };
int* numbers;
int* differentNumbers;
int* p;
int* otherNumbers;
void stepCounter(int a) {
// determines the step number of the number
if (a / 10 == 0)
stepCount = 1;
else if (a / 100 == 0)
stepCount = 2;
else if (a / 1000 == 0)
stepCount = 3;
else if (a / 10000 == 0)
stepCount = 4;
else if (a / 100000 == 0)
stepCount = 5;
else if (a / 1000000 == 0)
stepCount = 6;
else if (a / 10000000 == 0)
stepCount = 7;
else if (a / 100000000 == 0)
stepCount = 8;
else if (a / 1000000000 == 0)
stepCount = 9;
}
void stepIndicator(int b) {
// indicates each step of the number and pass them into array 'number'
stepCounter(b);
numbers = new int[stepCount];
for (i = stepCount; i>0; i--) {
//
/*
x = (round(pow(10,stepCount+1-i)));
y = (round(pow(10,stepCount-i)));
z = (round(pow(10,stepCount-i)));
*/
x = (int)(pow(10, stepCount + 1 - i) + 0.5);
y = (int)(pow(10, stepCount - i) + 0.5);
numbers[i - 1] = (b%x - b%y) / y;
}
}
int sameNumberCheck(int *array, int arraySize) {
//checks if the array has two or more of same integer inside return 1 if same numbers exist, 0 if not
for (i = 0; i<arraySize - 1; i++) {
//
for (j = i + 1; j<arraySize; j++) {
//
if (array[i] == array[j]) {
//
return 1;
}
}
}
return 0;
}
void getDifferentNumbers(int* array, int arraySize) {
//
k = 0;
j = 0;
checker = 0;
otherNumbers = new int[10 - arraySize]; //exact number of other numbers is 10 - numbers we have
for (i = 0; i<10; i++) {
if ((i>0)&(checker = 0)) {
k++;
otherNumbers[k - 1] = i - 1;
}
//
checker = 0;
for (j = 0; j<arraySize; j++) {
//
p = array + j;
cout << *p << endl; //ilkinde doğru sonra yanlış yapıyor?!
if (*p = i) {
checker++;
}
}
}
}
int main(int argc, char *argv[])
{
stepCounter(999999);
cout << stepCount << endl;
stepIndicator(826424563);
for (j = 0; j<9; j++) {
//
cout << numbers[j] << endl;
}
cout << sameNumberCheck(numstringTest, 10) << " must be 1" << endl;
cout << sameNumberCheck(numstring, 10) << " must be 0" << endl;
cout << endl;
getDifferentNumbers(numstringTest, 10);
cout << endl;
cout << endl << otherNumbers[0] << " is the diff number" << endl;
system("PAUSE");
return EXIT_SUCCESS;
}
Hi, my problem is with pointers actually. You will see above, function getDifferentNumbers. It simply does a comparement if in any given array there are repeated numbers(0-9). To do that, I passed a pointer to the function. I simply do the comparement via pointer. However, there is a strange thing here. When I execute, first time it does correct, but secon time it goes completely mad! This is the function:
void getDifferentNumbers(int* array, int arraySize) {
//
k = 0;
j = 0;
checker = 0;
otherNumbers = new int[10 - arraySize]; //exact number of other numbers is 10 - numbers we have
for (i = 0; i<10; i++) {
if ((i>0)&(checker = 0)) {
k++;
otherNumbers[k - 1] = i - 1;
}
//
checker = 0;
for (j = 0; j<arraySize; j++) {
//
p = array + j;
cout << *p << endl; //ilkinde doğru sonra yanlış yapıyor?!
if (*p = i) {
checker++;
}
}
}
}
and this is the array I passed into the function:
int numstringTest[10] = {0,1,2,3,4,5,6,7,7,9};
it should give the number 7 in otherNumbers[0], however it does not. And I do not know why. I really can not see any wrong statement or operation here. When I execute, it first outputs the correct values of
numstringTest: 1,2,3,4,5,6,7,7,9
but on next 9 iteration of for loop it outputs:
000000000011111111112222222222333333333344444444445555555555666666666677777777778888888888

Answer 1

You have some basic problems in your code.
There are multiple comparisons that are not really comparisons, they're assignments. See the following:
if((i>0) & (checker=0)){
and
if(*p = i){
In both cases you're assigning values to the variables, not comparing them. An equality comparison should use ==, not a single =. Example:
if (checker == 0) {
Besides that, you're using & (bitwise AND) instead of && (logical AND), which are completely different things. You most likely want && in your if statement.

Answer 2

I've just noticed this:
getDifferentNumbers(numstringTest, 10);
and in that function:
otherNumbers = new int[10 - arraySize];
which doesn't seem right.