What are some hacks to reduce the length of code written in C?

I will assume that you are doing this for some shortest code contest or have some other reason to reduce code size. Otherwise, do not try to reduce code length just because it feels cool. Verbosity is any day preferable to obfuscation. A few things that you could try will be: Make macros for repeating code blocks. If you are going to use scanf to read integers 10 times in your code, makes sense to define a macro S(x) that reads integers. But the thing is, the macro could be a substitute for any weird contraption, not just a function. For an example see http://www.codechef.com/viewsolution/456464. Use the conditional (?:) operator and nest it lavishly. In most of the cases, you should not need to have if/else in your code. If code length is the only constraint and you don't mind sacrificing some speed for the same, try to tinker with your program flow. Do more operations than required if it doesn't change the result and shortens the code. For example, adding zeros to a few corner case variables might be shorter than checking those corner case conditions. Use the fact that global variables are initialised to 0, and that main and its arguments are assumed to be ints (This could be a gcc specific thing, but if you are just looking for shortest code contests, that should do since most contest compilers are gcc) These are the tricks that I have seen to be used most commonly. WIll add anything further that I can think of.

1) Move the repetitive code to non-inline functions - reduces both hand-written and generated code size, if the function-calling overhead is not a concern. 2) Use short and intuitive variable name over unnecessary long ones -  just i over indexForTheLoopToIterate, etc. 3) Avoid explicit zero-initialization for local variables which are static, global variables which are either static or non-static. 4) Place the statements inside a loop which are exactly same except that they differ in using some sort of index, unless you have unrolled it already as a speed-up mechanism. 5) Prefer writing functions which perform simple evaluations, in a simple manner - just have the evaluation as part of the return statement; no need of extra temporary variables in the code Simple ex: int sub(int a, int b){ return a - b;} instead of int sub(int a, int b){ int ret = a - b; return ret;} 6) Avoid explicit checks for NULL. If a variable p is a pointer, then just if ( p ) is enough and exactly same as if ( p != NULL ). 7) Use ++ instead of + or += when possible. Same applies to --. 8) If you have bunch of generic functions which are supposedly having long/very long names, then hold their addresses in an array of function pointers and just index appropriately to call them. 9) Avoid explicit zero-initializing all the elements of a local non-static compile-time array(applies to char arrays as well when you require an empty string). Just initialize the first one and rest automatically gets initialized to zero. 10) Avoid temporary variables when you can - swapping integer variables using ^ or ^= keeping in mind the concept of sequence points. 11) Use += when possible: a += b instead of a = a + b. 12) Though no one uses ever, just for the sake of completeness I am mentioning this: no explicit unary-plus. +a is any day same as that of a and so on! 13) Use bit-fields to access individual bits of a byte instead of masking/shifting, unless portability of the code is a concern. 14) No extra comma(,) needed after the last element of an array or the last enum-specifier. That's all I can think of as of now! :) Choose the above optimizations with respect to the hand-written C code's size based on how intuitive they are to you and your intended audience. Any day, prefer readability over not-so-intuitive succinctness.

#define GETC ({char x;scanf("%c ", &x);x;}) #define GETL ({long x;scanf("%li\n", &x);x;}) long t=GETL; char c= GETC; instead of writing scanf every time u can use this one. If u create x as global variable, it will even more better in terms o saving memory.