不以“ THE”结尾的字符串的DFA

问题–接受不以子字符串“ THE”结尾的字符串。检查给定的字符串是否以“ the”结尾。字符串末尾避免使用的“ the”的不同形式为：

"THE", "ThE", "THe", "tHE", "thE", "The", "tHe" and "the"

所有以上述任何形式的“ the”结尾的字符串均不接受。

不以“ THE”结尾的字符串的确定性自动机(DFA)–
此dfa中的初始状态为Qo

程序中使用的方法–
在此程序中，请考虑4个状态分别为0、1、2和3。现在让我们接受一个名为DFA的变量，该变量最初将为0。无论何时发生任何转换，它都将使用与DFA相关的数字来更新DFA的值。新状态。

示例：如果发生从状态0到状态1的过渡，则DFA的值将更新为1。如果发生从状态2到状态3的过渡，则dfa的值将更新为3。整个字符串上的算法，如果最后达到状态0、1或2，则我们的字符串将被接受，否则将不被接受。

Input : XYzabCthe
Output : NOT ACCEPTED

Input :  Themaliktth
Output :  ACCEPTED

C++

// CPP program to implement DFS that accepts
// all string that do not end with "THE"
#include 
#include 
  
// dfa tells the number associated
// with the present state
int dfa = 0;
  
// This function is for
// the starting state (zeroth) of DFA
void start(char c)
{
    // On receiving 'T' or 't' goto first state (1)
    if (c == 't' || c == 'T')
        dfa = 1;
}
  
// This function is for the first state of DFA
void state1(char c)
{
    // On receiving 'T' or 't' goto first state (1)
    if (c == 't' || c == 'T')
        dfa = 1;
  
    // On receiving 'H' or 'h' goto second state (2)
    else if (c == 'h' || c == 'H')
        dfa = 2;
  
    // else goto starting state (0)
    else
        dfa = 0;
}
  
// This function is for the second state of DFA
void state2(char c)
{
    // On receiving 'E' or 'e' goto third state (3)
    // else goto starting state (0)
    if (c == 'e' || c == 'E')
        dfa = 3;
    else
        dfa = 0;
}
  
// This function is for the third state of DFA
void state3(char c)
{
    // On receiving 'T' or 't' goto first state (1)
    // else goto starting state (0)
    if (c == 't' || c == 'T')
        dfa = 1;
    else
        dfa = 0;
}
  
bool isAccepted(char str[])
{
    // store length of string
    int len = strlen(str);
  
    for (int i=0; i < len; i++) {
            if (dfa == 0)
                start(str[i]);
  
            else if (dfa == 1)
                state1(str[i]);
  
            else if (dfa == 2)
                state2(str[i]);
  
            else
                state3(str[i]);        
    }
  
    return (dfa != 3);
}
  
// driver code
int main()
{
    char str[] = "forTHEgeeks";
    if (isAccepted(str) == true)
        printf("ACCEPTED\n");
    else
        printf("NOT ACCEPTED\n");
    return 0;
}

Java

// Java program to implement DFS that accepts
// all string that do not end with "THE"
import java.util.*;
  
class GFG 
{
  
// dfa tells the number associated
// with the present state
static int dfa = 0;
  
// This function is for
// the starting state (zeroth) of DFA
static void start(char c)
{
    // On receiving 'T' or 't' goto first state (1)
    if (c == 't' || c == 'T')
        dfa = 1;
}
  
// This function is for the first state of DFA
static void state1(char c)
{
    // On receiving 'T' or 't' goto first state (1)
    if (c == 't' || c == 'T')
        dfa = 1;
  
    // On receiving 'H' or 'h' goto second state (2)
    else if (c == 'h' || c == 'H')
        dfa = 2;
  
    // else goto starting state (0)
    else
        dfa = 0;
}
  
// This function is for the second state of DFA
static void state2(char c)
{
    // On receiving 'E' or 'e' goto third state (3)
    // else goto starting state (0)
    if (c == 'e' || c == 'E')
        dfa = 3;
    else
        dfa = 0;
}
  
// This function is for the third state of DFA
static void state3(char c)
{
    // On receiving 'T' or 't' goto first state (1)
    // else goto starting state (0)
    if (c == 't' || c == 'T')
        dfa = 1;
    else
        dfa = 0;
}
  
static boolean isAccepted(char str[])
{
    // store length of string
    int len = str.length;
  
    for (int i=0; i < len; i++) 
    {
            if (dfa == 0)
                start(str[i]);
  
            else if (dfa == 1)
                state1(str[i]);
  
            else if (dfa == 2)
                state2(str[i]);
  
            else
                state3(str[i]);     
    }
  
    return (dfa != 3);
}
  
// Driver code
public static void main(String[] args)
{
    char str[] = "forTHEgeeks".toCharArray();
    if (isAccepted(str) == true)
        System.out.println("ACCEPTED\n");
    else
        System.out.println("NOT ACCEPTED\n");
}
}
  
/* This code is contributed by PrinciRaj1992 */

Python3

# Python3 program to implement DFS that accepts 
# all stringing that do not end with "THE" 
  
# This function is for the starting
# state (zeroth) of DFA 
def start(c):
      
    # On receiving 'T' or 't' goto 
    # first state (1) 
    if (c == 't' or c == 'T'):
        dfa=1
  
# This function is for the first state of DFA 
def state1(c): 
      
    # On receiving 'T' or 't' goto first state (1) 
    if (c == 't' or c == 'T'):
        dfa = 1
  
    # On receiving 'H' or 'h' goto second state (2) 
    elif (c == 'h' or c == 'H'):
        dfa = 2
  
    # else goto starting state (0) 
    else:
        dfa = 0
  
# This function is for the second state of DFA 
def state2(c):
      
    # On receiving 'E' or 'e' goto third 
    # state (3) else goto starting state (0) 
    if (c == 'e' or c == 'E'):
        dfa = 3
    else:
        dfa = 0
          
# This function is for the third state of DFA 
def state3(c):
      
    # On receiving 'T' or 't' goto first 
    # state (1) else goto starting state (0) 
    if (c == 't' or c == 'T'):
        dfa = 1
    else:
        dfa = 0
  
def isAccepted(string):
      
    # store length of stringing 
    length = len(string) 
  
    for i in range(length):
        if (dfa == 0):
            start(string[i])
        elif (dfa == 1):
            state1(string[i])
        elif (dfa == 2):
            state2(string[i])
        else:
            state3(string[i])         
    return (dfa != 3) 
  
# Driver Code 
if __name__ == "__main__" :
    string="forTHEgeeks"
      
    # dfa tells the number associated 
    # with the present state
    dfa = 0
    if isAccepted(string):
        print("ACCEPTED")
    else:
        print("NOT ACCEPTED")
  
# This code is contributed by SHUBHAMSINGH10

C#

// C# program to implement DFS that accepts
// all string that do not end with "THE"
using System;
  
class GFG
{
      
// dfa tells the number associated
// with the present state
static int dfa = 0;
  
// This function is for
// the starting state (zeroth) of DFA
static void start(char c)
{
    // On receiving 'T' or 't' goto first state (1)
    if (c == 't' || c == 'T')
        dfa = 1;
}
  
// This function is for the first state of DFA
static void state1(char c)
{
    // On receiving 'T' or 't' goto first state (1)
    if (c == 't' || c == 'T')
        dfa = 1;
  
    // On receiving 'H' or 'h' goto second state (2)
    else if (c == 'h' || c == 'H')
        dfa = 2;
  
    // else goto starting state (0)
    else
        dfa = 0;
}
  
// This function is for the second state of DFA
static void state2(char c)
{
    // On receiving 'E' or 'e' goto third state (3)
    // else goto starting state (0)
    if (c == 'e' || c == 'E')
        dfa = 3;
    else
        dfa = 0;
}
  
// This function is for the third state of DFA
static void state3(char c)
{
    // On receiving 'T' or 't' goto first state (1)
    // else goto starting state (0)
    if (c == 't' || c == 'T')
        dfa = 1;
    else
        dfa = 0;
}
  
static bool isAccepted(char []str)
{
    // store length of string
    int len = str.Length;
  
    for (int i=0; i < len; i++) 
    {
            if (dfa == 0)
                start(str[i]);
  
            else if (dfa == 1)
                state1(str[i]);
  
            else if (dfa == 2)
                state2(str[i]);
  
            else
                state3(str[i]); 
    }
  
    return (dfa != 3);
}
  
// Driver code
static public void Main ()
{
    char []str = "forTHEgeeks".ToCharArray();
    if (isAccepted(str) == true)
        Console.WriteLine("ACCEPTED\n");
    else
        Console.WriteLine("NOT ACCEPTED\n");
}
}
  
/* This code is contributed by ajit. */

输出 ：

ACCEPTED

该程序的时间复杂度为O(n)