Resources for Code Optimization Agner Optimizing Assembly Code
Sum Of Large Numbers In C
Write a program which can do sum of large numbers having up to 1000 digits Solution by Arjun Suresh
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#include <stdio.h> #include <string.h> #include <ctype.h> void print(char *a, int l); int read(char *a); int sum(char *a, char* b, char * c, int al, int bl); int main(void) { char a[1000], b[1000], c[1000]; //a and b hold the input numbers and c hold the output number. Each array entry is a digit int al, bl; //for storing the number of digits of the two input numbers printf("Enter the first number "); al = read(a); printf("Enter the second number "); bl = read(b); int l = sum(a, b, c, al, bl); printf("sum = "); print(c, l); return 0; } int sum(char *a, char* b, char * c, int al, int bl) { int l = al > bl? al:bl;//l stores the no.of digit of output which may become l+1 due to carry from MSB int i = l; char carry = 0; while(al > 0 && bl > 0) { char val = a[--al] + b[--bl] + carry; c[i--] = val % 10; carry = val / 10; } while(al > 0)//If a has more digits than b { char val = a[--al] + carry; c[i--] = val % 10; carry = val / 10; } while(bl > 0)//If b has more digits than a { char val = b[--bl] + carry; c[i--] = val % 10; carry = val / 10; } c[0] = carry;//Assigning the final carry return l+1;//Return the no. of digits of output } int read(char *a) { char c; int i = 0; do { c = getchar(); } while(isspace(c)); //Reading and discarding any whitespace char typed while(isdigit(c)) { a[i++] = c - 48; //getchar returns the ASCII. So, for 1 it returns 49. Subtracting 48, we get the actual int value entered via keyboard c = getchar(); } return i;//Return the no. of digits read } void print(char *a, int l) { int i; if(a[0] != 0) printf("%d", a[0]);//If final carry is 0, ignore it for(i = 1; i < l; i++) { printf("%d", a[i]); } printf("\n"); } |
SSH Without Password
The basis of this is that your ID must be in the list of authorized hosts in the server. So, for password-less login to work, generate your public key, and append it to the authorized_hosts file in the server. To create a public key, from terminal do
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ssh-keygen -t rsa |
To copy to authorized_hosts file do
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cat ~/.ssh/id_rsa.pub | ssh serveruser@server 'cat &gt;&gt; ~/.ssh/authorized_keys' |
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Useful Links for Programming Interviews
http://sixrevisions.com/resources/10-puzzle-websites-to-sharpen-your-programming-skills/ http://www.coderholic.com/10-more-puzzle-websites-to-sharpen-your-programming-skills/ http://comeoncodeon.wordpress.com/page/2/ http://tausiq.wordpress.com/ http://www.iarcs.org.in/inoi/contests/allproblems.php http://www.careercup.com/ https://www.interviewstreet.com/challenges/ https://www.facebook.com/ProgrammingInterviews http://blog.seattleinterviewcoach.com/2009/02/140-google-interview-questions.html http://www.cse.iitd.ernet.in/~sbaswana/Puzzles/Algo/algo.html http://www.comp.nus.edu.sg/~stevenha/programming/vol1.html http://www1.cs.columbia.edu/~kns10/interview/ http://concentratedlemonjuice.blogspot.com/2008/05/puzzles_4358.html
Some Reduction Inferences
How to solve problems by reduction?