设计一个函数模版find，用于对一个有序数组采用二分法查找指定数据的元素下标，用int, char型数据测试完整代码

下面是一个实现二分查找的函数模板 `find`，使用了 C++ 的迭代器（iterator）来遍历数组：

#include <iostream>
#include <vector>

template<typename T>
int find(const std::vector<T>& arr, const T& target) {
    int left = 0;
    int right = arr.size() - 1;
    while (left <= right) {
        int mid = (left + right) / 2;
        if (arr[mid] == target) {
            return mid;
        } else if (arr[mid] < target) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    return -1;
}

int main() {
    std::vector<int> arr1 = {1, 3, 5, 7, 9, 11, 13};
    int target1 = 7;
    int index1 = find(arr1, target1);
    if (index1 != -1) {
        std::cout << "Found " << target1 << " at index " << index1 << std::endl;
    } else {
        std::cout << "Could not find " << target1 << std::endl;
    }

    std::vector<char> arr2 = {'a', 'c', 'e', 'g', 'i', 'k', 'm'};
    char target2 = 'g';
    int index2 = find(arr2, target2);
    if (index2 != -1) {
        std::cout << "Found " << target2 << " at index " << index2 << std::endl;
    } else {
        std::cout << "Could not find " << target2 << std::endl;
    }

    return 0;
}

输出结果：

Found 7 at index 3
Found g at index 3

注意：这个函数模板要求输入的数组是有序的，否则可能得到错误的结果。