To participate in ICPC you have to find 2 other people that will be in your team Then you need to pass qualification stage that happens in September (it's maybe optional — depends on the region, idk) Then you go to 1/4 stage and if you good enough, you go to 1/2, then Finals To prepare, use codeforces.com
— And it's offtopic enough, so the topic is closed
— If you want to continue, go to the #ot chat
— The two following lines are the same?
int* ptr = (int*) malloc(sizeof(int)*4);
int* ptr = (int*) calloc(4, sizeof(int));
(except calloc set all the memory allocated to zero)