char leftchar des int size char src int count模型； 返回结果字符串指针用例的所有例子

模型： char* left(char* des, int size, char* src, int count);

返回结果字符串指针。

用例：

1. 输入：des = "abc", size = 10, src = "hello world", count = 5 预期输出：des = "hello", 返回值为指向des的指针

2. 输入：des = "", size = 5, src = "hello world", count = 8 预期输出：des = "hello wo", 返回值为指向des的指针

3. 输入：des = "12345", size = 6, src = "hello world", count = 0 预期输出：des = "12345", 返回值为指向des的指针

4. 输入：des = "abc", size = 3, src = "hello world", count = 5 预期输出：des = "hel", 返回值为指向des的指针

5. 输入：des = "abc", size = 4, src = "hello world", count = 20 预期输出：des = "hello world", 返回值为指向des的指针

6. 输入：des = "", size = 0, src = "hello world", count = 5 预期输出：des = "", 返回值为指向des的指