0
Want this question answered?
Be notified when an answer is posted
Add your answer:
Earn +20 pts
How do you write c program to identify keywords using transition table?
#include#include#includevoid keyw(char str[10]){if(strcmp("for",str)==0)printf("%s is a keyword",str);else if(strcmp("while",str)==0)printf("%s is a keyword",str);else if(strcmp("char",str)==0)printf("%s is a keyword",str);else if(strcmp("int",str)==0)printf("%s is a keyword",str);else if(strcmp("if",str)==0)printf("%s is a keyword",str);else if(strcmp("else",str)==0)printf("%s is a keyword",str);elseprintf("%s is an identifier",str);printf("\n");}main(){FILE *f1,*f2,*f3;char c,str[10];int num[100],ln=0,tvalue=0,i=0,j=0,k=0;printf("Enter a C program expression");f1=fopen("input.c","w");while((c=getchar())!=EOF)fputc(c,f1);f1=fopen("input.c","r");f2=fopen("identifier.txt","w");f3=fopen("specialchars.txt","w");while((c=fgetc(f1))!=EOF){if(isdigit(c)){tvalue=c-'0';c=fgetc(f1);while(isdigit(c)){tvalue=tvalue*10+c-'0';c=fgetc(f1);}num[i++]=tvalue;ungetc(c,f1);}else if(isalpha(c)){fputc(c,f2);c=fgetc(f1);while((isdigit(c))isalpha(c)c==' 'c=='$'){fputc(c,f2);c=fgetc(f1);}fputc(' ',f2);ungetc(c,f1);}else if(c==' 'c=='\t');else if(c=='\n')ln++;elsefputc(c,f3);}fclose(f1);fclose(f2);fclose(f3);printf("Numbers in the program are \n");for(j=0;j
Write a c plus plus program of array to pointers?
#include voidprintarr(inta[]);voidprintdetail(inta[]);main(){inta[5];for(inti = 0;i
How do you swap 2 variables without using third variable?
void main() { int a,b; clrscr(); printf("\n\n\t\tenter any two nos..."); scanf("%d%d",&a,&b); a=a+b; b=a-b; a=a-b; printf("\n\n\t\tvalue of a=",a); printf("\n\n\t\tvalue of b=",b); getch(); }
How do you display the contents of the memory address stored in an element of a pointer array?
Remember that a pointer is just a variable containing the memory address of another variable. A pointer to a pointer is no different, other than that the address contains the address of another pointer. You use the * indirection operator to get the value of the variable being pointed at (the address of the other pointer), and the ** indirection operator to get at the value pointed at by the other pointer. The following example illustrates how to access the values of pointers to int via an array of pointers to those pointers. The memory address and the value of every variable is displayed for the benefit of clarity. #include <iostream> using namespace std; int main() { // Set up an array of pointers to pointers to int variables. int X = 1, Y=2; // The actual variables. int* pX = &X; // Pointers to those variables int* pY = &Y; int** pp[2]; // Array of pointers to those pointers. pp[0] = &pX; pp[1] = &pY; // Print the address of all variables and their stored values: cout << "Var\t&Address\tValue" << endl; cout << "---\t--------\t-----" << endl; cout << "X\t0x" << &X << "\t" << X << endl; cout << "Y\t0x" << &Y << "\t" << Y << endl; cout << "pX\t0x" << &pX << "\t0x" << pX << endl; cout << "pY\t0x" << &pY << "\t0x" << pY << endl; cout << "pp\t0x" << &pp << "\t0x" << pp << endl; cout << endl; cout << "Note that both &pp and pp return the same value: the address of the array." << endl; cout << "pp is simply an alias for the memory allocated to the array itself, it is" << endl; cout << "not a variable that contains a value. You must access the elements of the" << endl; cout << "array to get at the actual values stored in the array." << endl; cout << endl; // Use the array elements to access the pointers and the values they point to: cout << "Elem\t&Address\tValue\t\t*Value\t\t**Value" << endl; cout << "----\t--------\t-----\t\t------\t\t-------" << endl; cout << "pp[0]\t0x" << &pp[0] << "\t0x" << pp[0] << "\t0x" << *pp[0] << "\t" << **pp[0] << endl; cout << "pp[1]\t0x" << &pp[1] << "\t0x" << pp[1] << "\t0x" << *pp[1] << "\t" << **pp[1] << endl; cout << endl; return( 0 ); }
Comparing the greedy approach alogorithm and the backtracking algorithm for the 0-1 knapsack problem with example?
1
How do you write a c program for hashing?
- Hashing is the transformation of a string of characters into a usually shorter fixed-length value or key that represents the original string. Hashing is used to index and retrieve items in a database because it is faster to find the item using the shorter hashed key than to find it using the original value. It is also used in many encryption algorithms. As a simple example of the using of hashing in databases, a group of people could be arranged in a database like this: Abernathy, Sara Epperdingle, Roscoe Moore, Wilfred Smith, David (and many more sorted into alphabetical order) Each of these names would be the key in the database for that person's data. A database search mechanism would first have to start looking character-by-character across the name for matches until it found the match (or ruled the other entries out). But if each of the names were hashed, it might be possible (depending on the number of names in the database) to generate a unique four-digit key for each name. For example: 7864 Abernathy, Sara 9802 Epperdingle, Roscoe 1990 Moore, Wilfred 8822 Smith, David (and so forth) A search for any name would first consist of computing the hash value (using the same hash function used to store the item) and then comparing for a match using that value. It would, in general, be much faster to find a match across four digits, each having only 10 possibilities, than across an unpredictable value length where each character had 26 possibilities. The hashing algorithm is called the hash function (and probably the term is derived from the idea that the resulting hash value can be thought of as a "mixed up" version of the represented value). In addition to faster data retrieval, hashing is also used to encrypt and decrypt digital signatures (used to authenticate message senders and receivers). The digital signature is transformed with the hash function and then both the hashed value (known as a message-digest) and the signature are sent in separate transmissions to the receiver. Using the same hash function as the sender, the receiver derives a message-digest from the signature and compares it with the message-digest it also received. They should be the same. The hash function is used to index the original value or key and then used later each time the data associated with the value or key is to be retrieved. Thus, hashing is always a one-way operation. There's no need to "reverse engineer" the hash function by analyzing the hashed values. In fact, the ideal hash function can't be derived by such analysis. A good hash function also should not produce the same hash value from two different inputs. If it does, this is known as a collision. A hash function that offers an extremely low risk of collision may be considered acceptable. Here are some relatively simple hash functions that have been used: * The division-remainder method: The size of the number of items in the table is estimated. That number is then used as a divisor into each original value or key to extract a quotient and a remainder. The remainder is the hashed value. (Since this method is liable to produce a number of collisions, any search mechanism would have to be able to recognize a collision and offer an alternate search mechanism.) * Folding: This method divides the original value (digits in this case) into several parts, adds the parts together, and then uses the last four digits (or some other arbitrary number of digits that will work ) as the hashed value or key. * Radix transformation: Where the value or key is digital, the number base (or radix) can be changed resulting in a different sequence of digits. (For example, a decimal numbered key could be transformed into a hexadecimal numbered key.) High-order digits could be discarded to fit a hash value of uniform length. * Digit rearrangement: This is simply taking part of the original value or key such as digits in positions 3 through 6, reversing their order, and then using that sequence of digits as the hash value or key. A hash function that works well for database storage and retrieval might not work as for cryptographic or error-checking purposes. There are several well-known hash functions used in cryptography. These include the message-digest hash functions MD2, MD4, and MD5, used for hashing digital signatures into a shorter value called a message-digest, and the Secure Hash Algorithm (SHA), a standard algorithm, that makes a larger (60-bit) message digest and is similar to MD4.
