一个单词表存放了五个表示颜色的英文单词，输入一个字母，在单词表中查找并输出所有以此字母开头的单词，若没有找到，输出Not Found。要求用指针数组和二级指针实现。

使用指针数组实现：

#include <iostream>
#include <cstring>
using namespace std;

int main() {
    char colors[5][10] = {"red", "green", "blue", "yellow", "black"};
    char letter;
    cout << "Enter a letter: ";
    cin >> letter;
    bool found = false;
    for (int i = 0; i < 5; i++) {
        if (colors[i][0] == letter) {
            found = true;
            cout << colors[i] << endl;
        }
    }
    if (!found) {
        cout << "Not Found" << endl;
    }
    return 0;
}

使用二级指针实现：

#include <iostream>
#include <cstring>
using namespace std;

int main() {
    char colors[5][10] = {"red", "green", "blue", "yellow", "black"};
    char letter;
    cout << "Enter a letter: ";
    cin >> letter;
    bool found = false;
    char **ptr = colors;
    for (int i = 0; i < 5; i++) {
        if (*ptr[0] == letter) {
            found = true;
            cout << *ptr << endl;
        }
        ptr++;
    }
    if (!found) {
        cout << "Not Found" << endl;
    }
    return 0;
}