C/Data Type/Array Int
Содержание
- 1 Allocate memory for int array
- 2 An example of how to initialize a matrix: loop
- 3 an example of using an array for two tasks
- 4 Array: assign and retrieve value
- 5 Array initialization
- 6 Assign int value reference to int array
- 7 Declares a 100-integer array
- 8 Define array and use it
- 9 Define int array and assign value
- 10 how to use arrays with functions
- 11 Int array and its pointer
- 12 Output array address
- 13 Prints out numbers and their doubles
- 14 Reference element in array
- 15 Shows two ways an array can be cleared
- 16 Use for loop to calculate the square and save it to array
Allocate memory for int array
#include <stdio.h>
#include <malloc.h>
main() {
int *base;
int i;
int j;
int cnt=0;
int sum=0;
printf("how many integers you have to store \n");
scanf("%d",&cnt);
base = (int *)malloc(cnt * sizeof(int));
printf("the base of allocation is %16lu \n",base);
if(!base)
printf("unable to allocate size \n");
else {
for(j = 0; j < cnt; j++)
*(base+j)=5;
}
sum = 0;
for(j = 0; j < cnt; j++)
sum = sum + *(base+j);
printf("total sum is %d\n",sum);
free(base);
printf("addr of allocation is %16lu \n",base);
base = (int *)malloc(cnt * sizeof(int));
printf("the base of allocation is %16lu \n",base);
base = (int *)malloc(cnt * sizeof(int));
printf("the base of allocation is %16lu \n",base);
base = (int *)calloc(10,2);
printf("the base of allocation is %16lu \n",base);
}
An example of how to initialize a matrix: loop
#define X_SIZE 60
#define Y_SIZE 30
int main()
{
int matrix[X_SIZE][Y_SIZE];
int x,y; /* current element to zero */
for (x = 0; x < X_SIZE; ++x) {
for (y = 0; y < Y_SIZE; ++y) {
matrix[x][y] = -1;
}
}
return (0);
}
an example of using an array for two tasks
#include <stdio.h>
int main() {
int temps[31];
int i, total;
float average,celsius;
total=0.0;
for( i = 0; i < 31; i++) {
printf("enter temperature #%d:", i);
scanf("%d", &temps[i]);
}
for(i = 0; i < 31; i++)
total += temps[ i ];
average = total / 31.0;
printf("average is:%f\n\n", average);
puts("fahrenheit \t celsius\n");
for( i = 0; i < 31; i++) {
celsius = (5.0 / 9.0) * ( temps[ i ] - 32);
printf("%d\t\t%6.2f\n", temps[ i ], celsius);
}
}
Array: assign and retrieve value
#include <stdio.h>
int main() {
int i = 0;
int a[5];
for(i = 0;i<5;i++) {
a[i]=i;
}
for( i = 0;i<5;i++) {
printf(" %d\n",a[i]);
}
}
Array initialization
#include <stdio.h>
int array[] = {3, 2, 1, 3, 6, 4, 2, 2, 9, 3};
int index;
int main()
{
index = 0;
while (array[index] != 0)
++index;
printf("Number of elements before zero %d\n",
index);
return (0);
}
Assign int value reference to int array
#include <stdio.h>
void printarr(int *a[]);
void printarr_usingptr(int *a[]);
int *a[5];
main() {
int i1=4,i2=3,i3=2,i4=1,i5=0;
int i;
int j;
a[0]=&i1;
a[1]=&i2;
a[2]=&i3;
a[3]=&i4;
a[4]=&i5;
printarr(a);
printarr_usingptr(a);
}
void printarr(int *a[]) {
int j;
printf("Address in array Value\n");
for(j = 0;j < 5;j++) {
printf("%16u %16u %d\n",a[j],a[j],a[j]);
}
}
void printarr_usingptr(int *a[]) {
int j = 0;
printf("using pointer\n");
for( j=0;j<5;j++) {
printf("value of elements %d %16lu %16lu\n",**a,*a,a);
a++;
}
}
Declares a 100-integer array
#include <stdio.h>
int main(void)
{
int x[100];
int i;
/* load x with values 0 through 99 */
for(i = 0; i < 100; ++i)
x[ i ] = i;
/* display contents of x */
for(i = 0; i < 100; ++i)
printf("%d ", x[ i ]);
return 0;
}
Define array and use it
#include <stdio.h>
void main()
{
int numbers[10]; /* Array storing 10 values */
int count = 10; /* Number of values to be read */
long sum = 0L; /* Sum of the numbers */
float average = 0.0f; /* Average of the numbers */
int i = 0; /* Loop counter */
printf("\nEnter the 10 numbers:\n");
/* Read the ten numbers to be averaged */
for(i = 0; i < count; i ++)
{
printf("%2d : ",i+1);
scanf("%d", &numbers[i]); /* Read a number */
sum += numbers[i]; /* Add it to sum */
}
average = (float)sum/count; /* Calculate the average */
printf("Average of the ten numbers entered is: %f\n", average);
}
Define int array and assign value
#include <stdio.h>
int main(void)
{
int a1[10], a2[10];
int i;
for(i = 1; i < 11; i++)
a1[ i - 1 ] = i;
for( i = 0; i < 10; i++)
a2[ i ] = a1[ i ];
for( i = 0; i < 10; i++)
printf("%d ", a2[ i ]);
return 0;
}
how to use arrays with functions
#include <iostream>
using namespace std;
#define iSIZE 5
void vadd_1(int iarray[]);
main( )
{
int iarray[iSIZE]={0,1,2,3,4};
int i;
cout << "iarray before calling add_1:\n\n";
for(i=0; i < iSIZE; i++)
cout << " " << iarray[i];
vadd_1(iarray);
cout << "\n\niarray after calling vadd_1:\n\n";
for(i=0; i < iSIZE; i++)
cout << " " << iarray[i];
return(0);
}
void vadd_1(int iarray[])
{
int i;
for(i=0; i < iSIZE; i++)
iarray[i]++;
}
Int array and its pointer
#include <stdio.h>
int main(void)
{
int a[10] = {10, 20, 30, 40, 50, 60, 70, 80, 90, 100};
int *p;
p = a; /* assign p the address of start of array a */
/* output a"s first, second and third elements using pointer */
printf("%d %d %d\n", *p, *(p+1), *(p+2));
/* this does the same thing using a */
printf("%d %d %d", a[0], a[1], a[2]);
return 0;
}
Output array address
#include <stdio.h>
void print_addr(int a[]);
main() {
int a[5];
int i;
for(i = 0;i<5;i++) {
a[i]=i;
}
print_addr(a);
}
void print_addr(int a[]) {
int *b;
int i;
b = a;
for(i = 0;i < 5; i++) {
printf("value %d and address is %16lu\n",*b,b);
b++;
}
}
Prints out numbers and their doubles
int main()
{
int data[10];
int twice[10];
int index;
for (index = 0; index < 10; ++index) {
data[index] = index;
twice[index] = index * 2;
}
return (0);
}
Reference element in array
#include <stdio.h>
char s[80];
int main(void)
{
s[3] = "X";
printf("%c", s[3]);
return 0;
}
Shows two ways an array can be cleared
#define MAX 10
void init_array_1(int data[]) {
int index;
for (index = 0; index < MAX; ++index)
data[index] = 0;
}
void init_array_2(int *data_ptr) {
int index;
for (index = 0; index < MAX; ++index)
*(data_ptr + index) = 0;
}
int main()
{
int array[MAX];
init_array_1(array);
init_array_1(&array[0]);
init_array_2(array);
return (0);
}
Use for loop to calculate the square and save it to array
#include <stdio.h>
int main(void)
{
int sqrs[ 10 ];
int i;
for(i = 1; i < 11; i++)
sqrs[ i - 1 ] = i * i ;
for(i = 0; i < 10; i++)
printf( "%d ", sqrs[ i ] );
return 0;
}