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## C Program to Sort Strings in Lexicographical Order In computer science, **lexicographical order** (also known as alphabetical or dictionary order) is the generalization of the alphabetical order of the dictionaries to sequences of ordered symbols. Sorting strings lexicographically is a fundamental operation in C programming. This tutorial demonstrates how to accept a list of strings from the user and sort them in alphabetical order using standard library functions. --- ### Understanding the Core Concepts To sort strings in C, we rely on two key functions provided by the `` header file: 1. **`strcmp(str1, str2)`**: Compares two strings character by character based on their ASCII values. - Returns `< 0` if `str1` is lexicographically smaller than `str2`. - Returns `0` if `str1` is equal to `str2`. - Returns `> 0` if `str1` is lexicographically larger than `str2`. 2. **`strcpy(dest, src)`**: Copies the content of the source string (`src`) to the destination buffer (`dest`). This is used to swap strings during the sorting process. --- ### Code Example: Sorting 10 Words Alphabetically The following program prompts the user to enter 10 words, sorts them in ascending lexicographical order using the Bubble Sort algorithm, and displays the sorted list. ```c #include #include int main() { int i, j; // Declare a 2D char array to store 10 strings, each up to 49 characters + null terminator char str, temp; printf("Enter 10 words:\n"); // Read 10 strings from the user for(i = 0; i < 10; ++i) { scanf("%s", str); } // Perform Bubble Sort to arrange strings lexicographically for(i = 0; i < 9; ++i) { for(j = i + 1; j < 10; ++j) { // If the current string is lexicographically greater than the next string, swap them if(strcmp(str, str) > 0) { strcpy(temp, str); strcpy(str, str); strcpy(str, temp); } } } printf("\nIn lexicographical order:\n"); for(i = 0; i < 10; ++i) { puts(str); } return 0; } ``` --- ### Sample Input and Output #### Input: ```text Enter 10 words: C C++ Java PHP Python Perl Ruby R JavaScript PHP ``` #### Output: ```text In lexicographical order: C C++ Java JavaScript PHP PHP Perl Python R Ruby ``` --- ### Code Explanation 1. **Two-Dimensional Array (`char str`)**: We define a 2D array where `10` represents the maximum number of strings, and `50` represents the maximum length of each string (including the null terminator `\0`). 2. **Comparison (`strcmp`)**: The nested loops compare adjacent elements. If `strcmp(str, str) > 0`, it means `str` should appear after `str` in alphabetical order. 3. **Swapping (`strcpy`)**: Because arrays in C cannot be directly assigned using the `=` operator (e.g., `str = str` is invalid), we must use `strcpy()` to copy the string data into a temporary buffer (`temp`) to complete the swap. --- ### Key Considerations & Best Practices * **Case Sensitivity**: The `strcmp()` function is case-sensitive because it compares ASCII values. In ASCII, all uppercase letters (`A-Z`, values `65-90`) come before lowercase letters (`a-z`, values `97-122`). For example, `"Zebra"` will be sorted *before* `"apple"`. To perform a case-insensitive sort, you can use platform-specific functions like `strcasecmp()` (POSIX) or `_stricmp()` (Windows). * **Buffer Overflow Prevention**: Using `scanf("%s", str)` can be unsafe if the user inputs a word longer than 49 characters. To prevent buffer overflows, you can limit the input size using a width specifier: `scanf("%49s", str)`. * **Handling Spaces**: `scanf("%s")` stops reading when it encounters whitespace. If you need to sort sentences or strings containing spaces, use `fgets(str, sizeof(str), stdin)` instead.