递归函数和main函数

Question

 用递归的形式写一个函数，用来判断一个字符串中的字符是否升序排列。例如，对于字符串“abcdefg”，函数返回true，对于字符串“abcedfg”返回false，对于一个空字符串，返回true。同样编写main函数来验证该函数的正确性。你可以假设输入都是小写字符。

Answer 1

返回true类型，需要使用stdbool头文件，并需要编译器支持c99。下面的程序没有问题，若报错则说明你的IDE不支持C99。#include<stdio.h> #include<string.h> #include<stdbool.h> bool isUpper(char * str, int start) { if(str[start + 1] == '\0' || strlen(str) == 0) { return true; } else if(str[start + 1] <= str[start]) { return false; } else { return isUpper(str, start + 1); } } int main() { char str[] = "abcdefg"; if(isUpper(str, 0)) { printf("是升序"); } else { printf("非升序"); } return 0; }

Answer 2

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