My aipo 2013 solutions

q1.c

#include <stdio.h>
#include <string.h>
#include <stdbool.h>

unsigned t(char a){
	return (unsigned)(a-48);
}

int main(void){
	char d[13];
	unsigned count = 0;
	char tmp;
	bool a, doom = false;
	unsigned i;
	unsigned to;
	unsigned gs = 0; //Gropus
	unsigned gcount = 0;
	
	//Spaghetti code a'la C
	while((tmp = getchar()) != EOF){
		if(tmp != '-' && tmp != ' ' && tmp != '\n'){
			d[count++] = tmp;
		}else if(tmp != '\n'){
			if(gcount==count){
				doom = true;
			}
			if(gs==0){
				if(count!=3){
					doom = true;
				}
			}
			
			gcount = count;
			++gs;
		}
		
		if(tmp == '\n'){
		
			if(d[0]=='9' && d[1]=='7' && (d[2]=='8' || d[2]=='9') && gs==4 && !doom && count == 13){
				a = false;
				to = 0;
				i = 0;
				for(; i< 12; ++i, a = !a){
					if(a){
						to += t(d[i])*3;
					}else{
						to += t(d[i]);
					}
				}
	
				printf("%u\n",((10 - (to % 10)) % 10 ) == t(d[12]) ? 1 : 0   );
			}else{
				printf("0\n");
			}
			count = 0;
			gs = 0;
			doom = false;
		}
	}
	
	return 0;
}

q2.c

#include <stdio.h>
#include <math.h>
#include <stdbool.h>

//Over-complicated but I was debugging. Blame it on Gary
bool appToParis(unsigned self[3][2], unsigned len, unsigned val1, unsigned val2){
	unsigned i = 0;
	for(i = 0; i<len; ++i){
		if((self[i][0] == val1 && self[i][1] == val2) || (self[i][0] == val2 && self[i][1] == val1)){
			return false;
		}
	}
	self[len][0] = val1;
	self[len][1] = val2;
	return true;
}

int main(void){
	unsigned num; //to be found
	unsigned found = 0; //found already
	unsigned total; //resukls to check
	unsigned first; //x
	float tmp; //sqrt res
	unsigned last = 0; //last num
	unsigned lastn = 0; //number itself
	
	
	unsigned pairs[3][2];
	unsigned pairl = 0;
	
	scanf("%u",&num);
	
	for(total = 3; found < num; ++total){
		for(first = 3; first < total; ++first){
				tmp = sqrt(total*total - first*first);
				if((int)tmp == tmp){
					if(lastn == total){
						pairl += appToParis(pairs, pairl, first, (unsigned)tmp);
						if(pairl > 1){
							//printf("\t%u. (%u, %f, %u)\n",found, first,tmp,total);
							///printf("%u^2 + %f^2 = %u^2\n",first,tmp,total);
							printf("%u\n",total);
							break;
						}
					}else{
						++found;
						lastn = total;
						pairl = 0;
						last = 0;
					}
					//printf("\t%u. (%u, %f, %u)\n",found, first,tmp,total);
				}
		}
	}
	return 0;
}

q3.c

#include <stdio.h>
#include <stdlib.h>
#define uns unsigned

int comp(uns *a, uns *b){
	return (*a) > (*b);
}

int main(void){
	//get length
	uns len, *arr = 0, i;
	scanf("%u",&len);
	//and allocate
	arr = malloc(sizeof(uns)*len);
	//and take down
	for(i = 0; i< len; ++i){
		scanf("%u", &(arr[i]));
	}
	
	//#arr = len
	qsort(arr,len,sizeof(uns),*comp);
	uns atmid, a, b, sol = 0;
	for(atmid = 0; atmid < len; ++atmid){
		for(a = 0; a <= atmid; ++a){
			for(b = atmid; b < len; ++b){
                                //How it that failing! All conditions should be met
				if(a != b && (arr[a]+arr[b])/2==arr[atmid] && (arr[a]+arr[b])%2==0){
					++sol;
				}
			}
		}
	}
	
	printf("%u\n", sol);
	//don't forgte to free
	free(arr);
	return 0;
}