实现字符串检索函数，该函数的功能是用来检索在一个指定的字符串中第一次出某个指定字符的位置。用指针和数组实现保存为 3.c-Achieve string retrieval function, which function is used to retrieve a specified string for the first time out of a specified character position. With pointers and arrays to achieve saved as 3.cpp