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  1. #include <stdio.h>
  2. #include <ctype.h>
  3. #include <string.h>
  4.  
  5. typedef struct {
  6.     char lexeme[100];
  7.     char type[20];
  8. } Token;
  9.  
  10. const char* keywords[] = {"int", "float", "if", "else", "while", "return", "void", "char", "for", "double"};
  11. const int num_keywords = sizeof(keywords) / sizeof(keywords[0]);
  12.  
  13. int isKeyword(const char* token) {
  14.     for (int i = 0; i < num_keywords; i++) {
  15.         if (strcmp(token, keywords[i]) == 0) return 1;
  16.     }
  17.     return 0;
  18. }
  19.  
  20. Token classifyToken(const char *token) {
  21.     Token t;
  22.     strcpy(t.lexeme, token);
  23.  
  24.     if (isKeyword(token))
  25.         strcpy(t.type, "KEYWORD");
  26.     else if (isdigit(token[0]))
  27.         strcpy(t.type, "NUMBER");
  28.     else if (isalpha(token[0]) || token[0] == '_')
  29.         strcpy(t.type, "IDENTIFIER");
  30.     else if (strchr("+-*/=<>!", token[0]))
  31.         strcpy(t.type, "OPERATOR");
  32.     else if (strchr(";(),{}", token[0]))
  33.         strcpy(t.type, "DELIMITER");
  34.     else
  35.         strcpy(t.type, "UNKNOWN");
  36.  
  37.     return t;
  38. }
  39.  
  40. void lexicalAnalyzer(const char *input) {
  41.     char token[100];
  42.     int index = 0;
  43.  
  44.     for (int i = 0; i < strlen(input); i++) {
  45.         char ch = input[i];
  46.  
  47.         if (isspace(ch)) {
  48.             if (index > 0) {
  49.                 token[index] = '\0';
  50.                 Token t = classifyToken(token);
  51.                 printf("%s: %s\n", t.type, t.lexeme);
  52.                 index = 0;
  53.             }
  54.         }
  55.         // Multi-character operators check
  56.         else if ((ch == '+' && input[i+1] == '=') ||
  57.                  (ch == '-' && input[i+1] == '=') ||
  58.                  (ch == '*' && input[i+1] == '=') ||
  59.                  (ch == '/' && input[i+1] == '=') ||
  60.                  (ch == '=' && input[i+1] == '=') ||
  61.                  (ch == '!' && input[i+1] == '=') ||
  62.                  (ch == '>' && input[i+1] == '=') ||
  63.                  (ch == '<' && input[i+1] == '=')) {
  64.             token[0] = ch;
  65.             token[1] = input[i+1];
  66.             token[2] = '\0';
  67.             Token t = classifyToken(token);
  68.             printf("%s: %s\n", t.type, t.lexeme);
  69.             i++; // skip next char
  70.         }
  71.         // Single-character operators or delimiters
  72.         else if (strchr("+-*/=<>!;(),{}", ch)) {
  73.             if (index > 0) {
  74.                 token[index] = '\0';
  75.                 Token t = classifyToken(token);
  76.                 printf("%s: %s\n", t.type, t.lexeme);
  77.                 index = 0;
  78.             }
  79.             token[0] = ch;
  80.             token[1] = '\0';
  81.             Token t = classifyToken(token);
  82.             printf("%s: %s\n", t.type, t.lexeme);
  83.         }
  84.         else {
  85.             token[index++] = ch;
  86.         }
  87.     }
  88.  
  89.     if (index > 0) {
  90.         token[index] = '\0';
  91.         Token t = classifyToken(token);
  92.         printf("%s: %s\n", t.type, t.lexeme);
  93.     }
  94. }
  95.  
  96. int main() {
  97.     char input[200];
  98.     printf("Enter a simple C code snippet: ");
  99.     fgets(input, sizeof(input), stdin);
  100.  
  101.     printf("\nTokens Found:\n");
  102.     lexicalAnalyzer(input);
  103.  
  104.     return 0;
  105. }
  106.  
Success #stdin #stdout 0s 5316KB
comments (?)
stdin
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+= -= /= *= == >= <= !=
stdout
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Enter a simple C code snippet: 
Tokens Found:
OPERATOR: +=
OPERATOR: -=
OPERATOR: /=
OPERATOR: *=
OPERATOR: ==
OPERATOR: >=
OPERATOR: <=
OPERATOR: !=
https://ideone.com/a4axDP
language:
C (gcc 8.3)
created:
7 hours ago
visibility:
public

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