I'm writing a code to split an array into 2 different ones, one with even numbers and one with odd numbers. I read the numbers from a file, put it all into an array, and get the split right. Here's the code where everything works:
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char** argv){
FILE* fpointer;
if (argc >= 2){
fpointer = fopen(argv[1], "r");
}else{
printf("No filename or multiple file names given");
return 0;
}
int numElem;
fscanf (fpointer, "%d\n", &numElem);
printf("Number of elements is %d\n", numElem);
int* arr;
int numEvens;
int numOdds;
arr = (int*) malloc(numElem*sizeof(int));
for (int i = 0; i < numElem; i++){
int temp;
fscanf(fpointer, "%d", &temp);
if(temp%2 == 0){
numEvens++;
}else{
numOdds++;
}
arr[i] = temp;
}
fclose(fpointer);
printf("number of evens: %d \n number of odds: %d\n", numEvens, numOdds);
//The array is now in "arr"
int* evens;
int* odds;
evens = (int*) malloc(numEvens*sizeof(int));
odds = (int*) malloc(numOdds*sizeof(int));
int a = 0;
int b = 0;
for (int i=0; i < numElem; i++){
printf("%d\n", arr[i]);
if (arr[i]%2 == 0){
evens[a] = arr[i];
a++;
}else{
odds[b] = arr[i];
b++;
}
}
printf("EVENS: %d\n", numEvens);
for (int i=0; i < numEvens; i++){
printf("%d\n", evens[i]);
}
printf("ODDS: %d\n", numOdds);
for (int i=0; i < numOdds; i++){
printf("%d\n", odds[i]);
}
Now I have a neat array with even numbers, and one with odd numbers. It outputs numEvens and numOdds correctly. Then I attempt to sort it:
int temp;
int x;
int y;
for (x = 0; x < numEvens-1; x++){
for (y=x+1; y < numEvens; y++){
if (evens[y] < evens[x]){
temp = evens[y];
evens[y] = evens[x];
evens[x] = temp;
}
}
}
return 0;
}
The output before I add in the sort method is:
Number of elements is 8
number of evens: 5
number of odds: 3
25
10
1
99
4
2
8
10
EVENS: 5
10
4
2
8
10
ODDS: 3
25
1
7
And the new output becomes:
Number of elements is 8
number of evens: 32772
number of odds: 1764530596
25
10
1
99
4
2
8
10
EVENS: 32772
10
4
2
8
10
0
0
0
0
....
The 0's go on presumably for another 32,000 times until I abort. I'm trying my hand at C after coming from java so memory allocation is a new subject for me, but I'm assuming it has something to do with that. I just don't understand how variables can be changed by lines of code added in after they are declared and printed. I don't really need help with new sorting methods, I just want some pointers on what's happening here so I can fix the errors. Thanks in advance!
