在一个程序中实现查找表的顺序查找与折半查找

下面是一个实现查找表的顺序查找与折半查找的示例程序：

#include <stdio.h>

// 定义查找表
int table[] = {1, 3, 5, 7, 9, 11, 13, 15, 17, 19};

// 顺序查找函数
int sequential_search(int key) {
    int i;
    for (i = 0; i < sizeof(table)/sizeof(int); i++) {
        if (table[i] == key) {
            return i;
        }
    }
    return -1;
}

// 折半查找函数
int binary_search(int key) {
    int left = 0, right = sizeof(table)/sizeof(int) - 1;
    while (left <= right) {
        int mid = (left + right) / 2;
        if (table[mid] == key) {
            return mid;
        } else if (table[mid] < key) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    return -1;
}

int main() {
    int key;
    printf("Enter the key to search: ");
    scanf("%d", &key);
    int index = sequential_search(key);
    if (index != -1) {
        printf("Sequential search: Found at index %d.\n", index);
    } else {
        printf("Sequential search: Not found.\n");
    }
    index = binary_search(key);
    if (index != -1) {
        printf("Binary search: Found at index %d.\n", index);
    } else {
        printf("Binary search: Not found.\n");
    }
    return 0;
}

该程序定义了一个查找表 `table`，包含了一些整数。顺序查找函数 `sequential_search` 从头到尾遍历表中的每个元素，直到找到目标元素或遍历完整个表。折半查找函数 `binary_search` 利用查找表已经有序的特点，进行二分查找。程序首先输入要查找的关键字，然后依次调用两个查找函数，输出查找结果。