和数组有关的选择结构和循环结构程序设计并运用if else语句、switch case语句、for语句、while语句及do while语句

以下是一个使用不同选择和循环结构的数组程序设计：

#include <stdio.h>

int main() {
    int arr[5] = {3, 7, 2, 1, 8};
    
    // if-else语句
    if(arr[0] < arr[1]) {
        printf("%d is less than %d\n", arr[0], arr[1]);
    }
    else {
        printf("%d is greater than or equal to %d\n", arr[0], arr[1]);
    }
    
    // switch-case语句
    switch(arr[2]) {
        case 1:
            printf("The value at index 2 is 1\n");
            break;
        case 2:
            printf("The value at index 2 is 2\n");
            break;
        case 3:
            printf("The value at index 2 is 3\n");
            break;
        default:
            printf("The value at index 2 is not 1, 2, or 3\n");
    }
    
    // for循环
    printf("The array contains: ");
    for(int i = 0; i < 5; i++) {
        printf("%d ", arr[i]);
    }
    printf("\n");
    
    // while循环
    int i = 0;
    while(i < 5) {
        printf("The value at index %d is %d\n", i, arr[i]);
        i++;
    }
    
    // do-while循环
    int j = 0;
    do {
        printf("The value at index %d is %d\n", j, arr[j]);
        j++;
    } while(j < 5);
    
    return 0;
}

输出：

3 is less than 7
The value at index 2 is 2
The array contains: 3 7 2 1 8 
The value at index 0 is 3
The value at index 1 is 7
The value at index 2 is 2
The value at index 3 is 1
The value at index 4 is 8
The value at index 0 is 3
The value at index 1 is 7
The value at index 2 is 2
The value at index 3 is 1
The value at index 4 is 8