Lexicographically Minimum String After Removing Stars - Solution & Explanation

This approach utilizes a stack data structure to keep track of characters in the string. As we iterate through the string, we push non-'*' characters onto the stack. When we encounter a '*', we pop from the stack, effectively removing the smallest character before the '*'. The stack allows us to maintain the remaining string in a way that can efficiently remove and process characters in a LIFO manner. Finally, we assemble our result from the characters remaining in the stack, which ensures the string is the lexicographically smallest possible after all required deletions.

The C code uses a dynamic character array as a stack to store non-'*' characters. As it iterates through the input string, it pushes characters onto the stack, and pops the stack when a '*' is encountered. The final stack content forms the result.

This approach leverages two pointers: one pointing to the current position in the input and another building the result in place. The fundamental idea is to overwrite the unnecessary characters in the array as we build the result string. We use the second pointer to track the last added character when we encounter a '*' and need to delete. After iterating through the entire input, the section of the array up to the second pointer will hold the resulting string.

This C code utilizes two pointers within the same array to process the characters. One advances through the input while the second adjusts the positions of meaningful characters, ensuring in-place modification of the string.