c语言中的sizeof运算符有什么用 如何用sizeof计算数组长度

#include <stdio.h>

int main() {
    int a = 10;
    float b = 3.14;
    char c = 'A';

    printf("Size of int: %zu bytes\n", sizeof(int));
    printf("Size of variable a: %zu bytes\n", sizeof(a));
    printf("Size of float: %zu bytes\n", sizeof(float));
    printf("Size of variable b: %zu bytes\n", sizeof(b));
    printf("Size of char: %zu bytes\n", sizeof(char));
    printf("Size of variable c: %zu bytes\n", sizeof(c));

    return 0;
}

#include <stdio.h>

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    size_t array_size = sizeof(arr); // 整个数组的大小
    size_t element_size = sizeof(arr[0]); // 数组中一个元素的大小
    size_t array_length = array_size / element_size; // 数组长度

    printf("Array size: %zu bytes\n", array_size);
    printf("Element size: %zu bytes\n", element_size);
    printf("Array length: %zu\n", array_length);

    return 0;
}

#include <stdio.h>

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    int *ptr = arr;

    printf("Size of pointer: %zu bytes\n", sizeof(ptr)); // 指针的大小
    printf("Size of int: %zu bytes\n", sizeof(int));     // int的大小

    return 0;
}

#include <stdio.h>

void print_array_length(int arr[]) {
    size_t array_size = sizeof(arr); // 实际上是指针的大小
    size_t element_size = sizeof(arr[0]); // 数组元素的大小
    size_t array_length = array_size / element_size; // 错误的数组长度

    printf("Array size in function: %zu bytes\n", array_size);
    printf("Element size in function: %zu bytes\n", element_size);
    printf("Array length in function: %zu\n", array_length);
}

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    print_array_length(arr);

    return 0;
}

#include <stdio.h>

void print_array_length(int arr[], size_t length) {
    printf("Array length in function: %zu\n", length);
}

int main() {
    int arr[] = {1, 2, 3, 4, 5};
    size_t array_length = sizeof(arr) / sizeof(arr[0]);
    print_array_length(arr, array_length);

    return 0;
}

#include <stdio.h>

struct MyStruct {
    char a;
    int b;
    char c;
};

union MyUnion {
    int a;
    double b;
};

int main() {
    printf("Size of MyStruct: %zu bytes\n", sizeof(struct MyStruct));
    printf("Size of MyUnion: %zu bytes\n", sizeof(union MyUnion));

    return 0;
}

#include <stdio.h>
#include <stdlib.h>

int main() {
    int *arr = (int *)malloc(5 * sizeof(int)); // 分配5个整数的空间

    if (arr == NULL) {
        printf("Memory allocation failed\n");
        return 1;
    }

    for (int i = 0; i < 5; i++) {
        arr[i] = i + 1;
    }

    for (int i = 0; i < 5; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");

    free(arr); // 释放内存
    return 0;
}

#include <stdio.h>

int main() {
    int int_array[] = {1, 2, 3, 4, 5};
    float float_array[] = {1.1, 2.2, 3.3, 4.4, 5.5};

    size_t int_length = sizeof(int_array) / sizeof(int_array[0]);
    size_t float_length = sizeof(float_array) / sizeof(float_array[0]);

    printf("Integer array length: %zu\n", int_length);
    printf("Float array length: %zu\n", float_length);

    return 0;
}

#include <stdio.h>

int main() {
    int n;
    printf("Enter the size of the array: ");
    scanf("%d", &n);

    int arr[n]; // 可变长数组

    printf("Size of VLA: %zu bytes\n", sizeof(arr));

    return 0;
}