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295 lines
10 KiB
C
295 lines
10 KiB
C
/*
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* C Program to Implements Regular Expression Matching
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*/
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#include <stdio.h>
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#include <string.h>
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#define MATCH printf("
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The Text Matches The Regular Expression");
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#define NOTMATCH printf("
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The Text Doesn't match the Regular Expression");
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char reg[20], text[20];
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int main()
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{
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int i, rlen, tlen, f = 0;
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char ans;
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do
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{
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printf("
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Enter the Regular Expression
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");
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scanf(" %[^
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]s", reg);
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for (rlen = 0; reg[rlen] != ''; rlen++);
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printf("
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Enter the text
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");
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scanf(" %[^
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]s", text);
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for (tlen = 0; text[tlen] != '' ; tlen++);
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if (reg[0] == '*')
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{
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printf("
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Invalid regular expression");
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}
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/*
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*If the regular expression starts with Alphabet
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*/
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if ((reg[0] >= 65 && reg[0] <= 90) || (reg[0] >= 97 && reg[0] <=122))
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{
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if (reg[0] == text [0])
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{
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switch (reg[1])
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{
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case '.' :
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switch (reg[2])
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{
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case '*':
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if (tlen != 1)
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{
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if (reg[3] == text[tlen-1])
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{
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MATCH;
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}
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else
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{
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NOTMATCH;
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}
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}
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else
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{
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NOTMATCH;
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}
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break;
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case '+':
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if (text[1] != reg[3])
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{
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if (reg[3] == text[tlen - 1])
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{
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MATCH;
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}
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else
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{
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NOTMATCH;
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}
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}
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break;
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case '?':
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if (text[1] == reg[3] || text[2] == reg[3])
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{
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if (text[1] == reg[3] || text[2] == reg[3])
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{
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MATCH;
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}
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else
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{
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NOTMATCH;
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}
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}
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else
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{
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NOTMATCH;
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}
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break;
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}
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break;
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case '*':
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if (reg[rlen-1] == text[tlen-1])
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{
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for (i = 0; i <= tlen-2; i++)
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{
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if(text[i] == reg[0])
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{
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f = 1;
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}
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else
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{
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f = 0;
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}
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}
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if ( f == 1)
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{
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MATCH;
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}
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else
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{
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NOTMATCH;
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}
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}
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else
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{
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NOTMATCH;
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}
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break;
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case '+' :
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if (tlen <= 2)
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{
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NOTMATCH;
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}
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else if (reg[rlen-1] == text[tlen-1])
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{
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for (i = 0; i < tlen-2; i++)
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{
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if (text[i] == reg[0])
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{
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f = 1;
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}
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else
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{
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f = 0;
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}
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}
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if (f == 1)
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{
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MATCH;
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}
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else
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{
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NOTMATCH;
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}
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}
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break;
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case '?':
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if (reg[rlen -1] == text[tlen-1])
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{
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MATCH;
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}
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else
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{
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NOTMATCH;
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}
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break;
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}
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}
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else
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printf("Does not match");
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}
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/*
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*If Regular Expression starts with '^'
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*/
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else if (reg[0] == '^')
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{
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if (reg[1] == text[0])
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{
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MATCH;
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}
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else
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{
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NOTMATCH;
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}
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}
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/*
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*If Regular Expression Ends with '$'
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*/
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else if (reg[rlen-1] == '$')
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{
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if (reg[rlen-2] == text[rlen-1])
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{
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MATCH;
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}
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else
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{
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NOTMATCH;
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}
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}
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else
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printf("Not Implemented");
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printf("
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Do you want to continue?(Y/N)");
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scanf(" %c", &ans);
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}
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while (ans == 'Y' || ans == 'y');
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}
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Enter the Regular Expression
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C.*g
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Enter the text
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Cprogramming
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The Text Matches The Regular Expression
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Do you want to continue?(Y/N)y
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Enter the Regular Expression
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C*g
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Enter the text
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Cprogramming
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The Text Doesn't match the Regular Expression
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Do you want to continue?(Y/N)y
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Enter the Regular Expression
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C?.*g
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Enter the text
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Cprogramming
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The Text Matches The Regular Expression
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Do you want to continue?(Y/N)y
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Enter the Regular Expression
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C.?g
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Enter the text
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Cprogramming
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The Text Doesn't match the Regular Expression
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Do you want to continue?(Y/N)y
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Enter the Regular Expression
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C.+g
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Enter the text
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Cprogramming
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The Text Matches The Regular Expression
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Do you want to continue?(Y/N)y
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Enter the Regular Expression
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C+g
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Enter the text
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Cprogramming
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The Text Doesn't match the Regular Expression
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Do you want to continue?(Y/N)y
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Enter the Regular Expression
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^C.*
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Enter the text
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Cprogramming
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The Text Matches The Regular Expression
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Do you want to continue?(Y/N)y
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Enter the Regular Expression
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^p.*
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Enter the text
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Cprogramming
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The Text Doesn't match the Regular Expression
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Do you want to continue?(Y/N)y
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Enter the Regular Expression
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C.*g$
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Enter the text
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Cprogramming
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The Text Matches The Regular Expression
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Do you want to continue?(Y/N)y
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Enter the Regular Expression
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C.*n$
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Enter the text
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Cprogramming
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The Text Doesn't match the Regular Expression
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Do you want to continue?(Y/N)n |