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#include <ctype.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_LENGTH 100

bool isDelimiter(char chr) {
    return (chr == ' ' || chr == '+' || chr == '-' || chr == '*' || chr == '/' || 
            chr == ',' || chr == ';' || chr == '%' || chr == '>' || chr == '<' || 
            chr == '=' || chr == '(' || chr == ')' || chr == '[' || chr == ']' || 
            chr == '{' || chr == '}');
}

bool isOperator(char chr) {
    return (chr == '+' || chr == '-' || chr == '*' || chr == '/' || 
            chr == '>' || chr == '<' || chr == '=');
}

bool isValidIdentifier(char *str) {
    return (str[0] != '0' && str[0] != '1' && str[0] != '2' && str[0] != '3' &&
            str[0] != '4' && str[0] != '5' && str[0] != '6' && str[0] != '7' &&
            str[0] != '8' && str[0] != '9' && !isDelimiter(str[0]) && !isOperator(str[0]));
}

bool isKeyword(char *str) {
    const char *keywords[] = {"auto", "break", "case", "char", "const", "continue", 
                              "default", "do", "double", "else", "enum", "extern", 
                              "float", "for", "goto", "if", "int", "long", "register", 
                              "return", "short", "signed", "sizeof", "static", "struct", 
                              "switch", "typedef", "union", "unsigned", "void", "volatile", 
                              "while"};
    for (int i = 0; i < sizeof(keywords) / sizeof(keywords[0]); i++) {
        if (strcmp(str, keywords[i]) == 0) {
            return true;
        }
    }
    return false;
}

bool isInteger(char *str) {
    if (str == NULL || *str == '\0') {
        return false;
    }
    int i = 0;
    while (isdigit(str[i])) {
        i++;
    }
    return str[i] == '\0';
}

char *getSubstring(char *str, int start, int end) {
    int subLength = end - start + 1;
    char *subStr = (char *)malloc((subLength + 1) * sizeof(char));
    strncpy(subStr, str + start, subLength);
    subStr[subLength] = '\0';
    return subStr;
}

int lexicalAnalyzer(char *input) {
    int left = 0, right = 0;
    int len = strlen(input);
    
    while (right <= len) {
        if (!isDelimiter(input[right]) && right < len) {
            right++;
        }

        if (isDelimiter(input[right]) || right == len) {
            if (right > left) {
                char *subStr = getSubstring(input, left, right - 1);

                if (isKeyword(subStr)) {
                    printf("Token: Keyword, Value: %s\n", subStr);
                } else if (isInteger(subStr)) {
                    printf("Token: Integer, Value: %s\n", subStr);
                } else if (isValidIdentifier(subStr)) {
                    printf("Token: Identifier, Value: %s\n", subStr);
                } else {
                    printf("Token: Unidentified, Value: %s\n", subStr);
                }

                free(subStr);
            }
            left = right + 1;
        }

        if (isOperator(input[right])) {
            printf("Token: Operator, Value: %c\n", input[right]);
            right++;
            left = right;
        }

        if (right < len) {
            right++;
        }
    }

    return 0;
}

int main() {
    char lex_input[MAX_LENGTH] = "int a = b + c";
    printf("For Expression \"%s\":\n", lex_input);
    lexicalAnalyzer(lex_input);
    printf("\n");

    char lex_input01[MAX_LENGTH] = "int x=ab+bc+30+switch+ 0y ";
    printf("For Expression \"%s\":\n", lex_input01);
    lexicalAnalyzer(lex_input01);
    return 0;
}