如何检查输入字符串是否包含大写和小写组合？

我想知道如何检查输入字符串是否包含大写和小写组合。之后打印一条语句以显示输入字符串包含大写和小写的组合。

第0步：你需要的变量

char* str;
int   i;
char  found_lower, found_upper;

第一步：遍历字符串

for (int i = 0; str[i] != '\0'; i++)

第二步：检测大小写字符

found_lower = found_lower || (str[i] >= 'a' && str[i] <= 'z')
found_upper = found_upper || (str[i] >= 'A' && str[i] <= 'Z')

第 3 步：合并结果

mixed_case = found_lower && found_upper

第 4 步（可选）突破for尽早以节省一些时间

if (found_lower && found_upper) break;

完整源代码（警告：未经测试）：

char is_mixed(char* str) {

    int   i;
    char  found_lower = false, found_upper = false;

    for (int i = 0; str[i] != '\0'; i++) {
        found_lower = found_lower || (str[i] >= 'a' && str[i] <= 'z');
        found_upper = found_upper || (str[i] >= 'A' && str[i] <= 'Z');

        if (found_lower && found_upper) break;
    }

    return (found_lower && found_upper);

}