CS 330 Lecture 12 – Arrays and malloc
February 17, 2012 by Chris Johnson. Filed under
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cs330, lectures, spring 2012.
Agenda
- a C makefile
- arrays
- strings
- dynamic allocation
- a stack API
Code
makefile
EXES = first arrays months
all: $(EXES)
$(EXES): %: %.c
gcc -o $@ -Wall -std=c99 $<
clean:
rm -f $(EXES)
arrays.c
#include <stdio.h>
#include <stdlib.h>
int average(int nums[], int len) {
int sum = 0;
for (int i = 0; i < len; ++i) {
sum += nums[i];
}
return sum / len;
}
int main(int argc, char **argv) {
int nums[] = {
10, 15, 30, 10, 15, 30
};
printf("average(nums, 6): %d\n", average(nums, 6));
printf("nums[<0-2>]: %d %d %d %d %d\n",
nums[0], nums[1], nums[2], nums[3], nums[4]);
printf("%d\n", 3[nums]);
return 0;
}
months.c
#include <stdio.h>
#include <stdlib.h>
int *get_days_in_months() {
int *dims = (int *) malloc(sizeof(int) * 12);
dims[0] = 31;
dims[1] = 28;
dims[2] = 31;
dims[3] = 30;
dims[4] = 31;
dims[5] = 30;
dims[6] = 31;
dims[7] = 31;
dims[8] = 30;
dims[9] = 31;
dims[10] = 30;
dims[11] = 31;
/* { */
/* 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 */
/* }; */
return dims;
}
void foobag() {
int a = rand();
int b = rand();
int c = rand();
int d = rand();
}
int main(int argc, char **argv) {
int *arr = get_days_in_months();
foobag();
printf("arr[<0-11>]: %d %d %d %d %d %d %d %d %d %d %d %d\n", arr[0], arr[1], arr[2], arr[3], arr[4], arr[5], arr[6], arr[7], arr[8], arr[9], arr[10], arr[11]);
free(arr);
printf("arr[<0-11>]: %d %d %d %d %d %d %d %d %d %d %d %d\n", arr[0], arr[1], arr[2], arr[3], arr[4], arr[5], arr[6], arr[7], arr[8], arr[9], arr[10], arr[11]);
return 0;
}
Haiku
Boy scouts are prepared.
“Cool rock. But my pockets! Full!
I’ll malloc new ones.”