Experiment-2.pptx:pattern matching program

Experiment-2.pptx:pattern matching program

• 1.
  Data Structures Lab[BCSL305] Department of CSE- Data Science
• 2.
  Program 2: Developa Program in C for the following operations on Strings a. Read a main String (STR), a Pattern String (PAT) and a Replace String (REP) b. Perform Pattern Matching Operation: Find and Replace all occurrences of PAT in STR with REP if PAT exists in STR. Report suitable messages in case PAT does not exist in STR Support the program with functions for each of the above operations. Don't use Built-in functions. Department of CSE- Data Science
• 3.
  Procedure Step 1: Input •Read STR (main string) • Read PAT (pattern to find) • Read REP (replacement string) Step 2: Initialization • Set i = 0 (index for STR) • Set j = 0 (index for ANS, the result string) • Set flag = 0 (to track if any match is found) Department of CSE- Data Science
• 4.
  Step 3: PatternMatching Loop • While STR[i] is not end of string: • Check if PAT matches at position i in STR • If match found: • Copy REP to ANS • Advance i by length of PAT • Set flag = 1 • If no match: •Copy current character from STR to ANS •Increment i and j Department of CSE- Data Science
• 5.
  Step 4: Output •If flag == 0, print "Pattern not found" • Else, print ANS as the modified string Department of CSE- Data Science
• 6.
  Program #include <stdio.h> void read(charSTR[], char PAT[], char REP[]); void match(const char STR[], const char PAT[], const char REP[], char ANS[]); int main() { char STR[100], PAT[100], REP[100], ANS[300]; read(STR, PAT, REP); match(STR, PAT, REP, ANS); return 0; } Department of CSE- Data Science
• 7.
  void read(char STR[],char PAT[], char REP[]) { printf("Enter the main string STR: "); gets(STR); printf("Enter the pattern string PAT: "); gets(PAT); printf("Enter the replace string REP: "); gets(REP); } Department of CSE- Data Science
• 8.
  void match(const charSTR[], const char PAT[], const char REP[], char ANS[]) { int i = 0, j = 0, k, m, flag = 0; while (STR[i] != '0') { m = i; k = 0; // Check for pattern match while (STR[m] == PAT[k] && PAT[k] != '0’) { m++; k++; } Department of CSE- Data Science
• 9.
  // If patternfound if (PAT[k] == '0') { flag = 1; k = 0; while (REP[k] != '0') { ANS[j++] = REP[k++]; } i = m; } else { ANS[j++] = STR[i++]; } } Department of CSE- Data Science
• 10.
  ANS[j] = '0';// Null-terminate result string if (flag == 0) printf("Pattern not found.n"); else printf("Resultant string is: %sn", ANS); } Department of CSE- Data Science