ProjectEulerC/problem11.c at master · rpringst/ProjectEulerC · GitHub

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#include <stdio.h>
#include <stdlib.h>
#include <time.h>

static const int max_index = 20;
static const int offset_index = 3;
static const int offset_index_shift = 4;
static const int data[20][20] =
        {{ 8, 2,22,97,38,15, 0,40, 0,75, 4, 5, 7,78,52,12,50,77,91, 8},
         {49,49,99,40,17,81,18,57,60,87,17,40,98,43,69,48, 4,56,62, 0},
         {81,49,31,73,55,79,14,29,93,71,40,67,53,88,30, 3,49,13,36,65},
         {52,70,95,23, 4,60,11,42,69,24,68,56, 1,32,56,71,37, 2,36,91},
         {22,31,16,71,51,67,63,89,41,92,36,54,22,40,40,28,66,33,13,80},
         {24,47,32,60,99, 3,45, 2,44,75,33,53,78,36,84,20,35,17,12,50},
         {32,98,81,28,64,23,67,10,26,38,40,67,59,54,70,66,18,38,64,70},
         {67,26,20,68, 2,62,12,20,95,63,94,39,63, 8,40,91,66,49,94,21},
         {24,55,58, 5,66,73,99,26,97,17,78,78,96,83,14,88,34,89,63,72},
         {21,36,23, 9,75, 0,76,44,20,45,35,14, 0,61,33,97,34,31,33,95},
         {78,17,53,28,22,75,31,67,15,94, 3,80, 4,62,16,14, 9,53,56,92},
         {16,39, 5,42,96,35,31,47,55,58,88,24, 0,17,54,24,36,29,85,57},
         {86,56, 0,48,35,71,89, 7, 5,44,44,37,44,60,21,58,51,54,17,58},
         {19,80,81,68, 5,94,47,69,28,73,92,13,86,52,17,77, 4,89,55,40},
         { 4,52, 8,83,97,35,99,16, 7,97,57,32,16,26,26,79,33,27,98,66},
         {88,36,68,87,57,62,20,72, 3,46,33,67,46,55,12,32,63,93,53,69},
         { 4,42,16,73,38,25,39,11,24,94,72,18, 8,46,29,32,40,62,76,36},
         {20,69,36,41,72,30,23,88,34,62,99,69,82,67,59,85,74, 4,36,16},
         {20,73,35,29,78,31,90, 1,74,31,49,71,48,86,81,16,23,57, 5,54},
         { 1,70,54,71,83,51,54,69,16,92,33,48,61,43,52, 1,89,19,67,48}};

_Bool negative_offset(int offset, int index){
    return ((index-offset) >= 0);
}

_Bool positive_offset(int size, int offset, int index){
    return ((index+offset) < size);
}

void compare_and_assign(int* max, int* current){
    if (*current > *max)
        *max = *current;
    *current = 1;
}

int main(int argc, char **argv){
    int* maxproduct = (int*) calloc(1, sizeof(int));
    int* currentproduct = (int*) calloc(1, sizeof(int));
    clock_t begin, end;
    _Bool i_neg, i_pos, j_neg, j_pos;

    for(int cycles=0; cycles<1000; cycles++){
        *maxproduct = 0;
        *currentproduct = 1;

        begin = clock();
        for (int i = 0; i < max_index; i++)
            for (int j = 0; j < max_index; j++){
                if (data[i][j] == 0)
                    continue;

                i_neg = negative_offset(offset_index, i);
                i_pos = positive_offset(max_index, offset_index, i);
                j_neg = negative_offset(offset_index, j);
                j_pos = positive_offset(max_index, offset_index, j);

                //North
                if (i_neg){
                    for (int k=0; k<offset_index_shift; k++)
                        (*currentproduct)*=data[i-k][j];
                    compare_and_assign(maxproduct, currentproduct);
                }

                //Northeast
                if (i_neg && j_pos){
                    for (int k=0; k<offset_index_shift; k++)
                        (*currentproduct)*=data[i-k][j+k];
                    compare_and_assign(maxproduct, currentproduct);
                }

                //East
                if (j_pos){
                    for (int k=0; k<offset_index_shift; k++)
                        (*currentproduct)*=data[i][j+k];
                    compare_and_assign(maxproduct, currentproduct);
                }

                //Southeast
                if (i_pos && j_pos){
                    for (int k=0; k<offset_index_shift; k++)
                        (*currentproduct)*=data[i+k][j+k];
                    compare_and_assign(maxproduct, currentproduct);
                }

                //South
                if (i_pos){
                    for (int k=0; k<offset_index_shift; k++)
                        (*currentproduct)*=data[i+k][j];
                    compare_and_assign(maxproduct, currentproduct);
                }

                //Southwest
                if (i_pos && j_neg){
                    for (int k=0; k<offset_index_shift; k++)
                        (*currentproduct)*=data[i+k][j-k];
                    compare_and_assign(maxproduct, currentproduct);
                }

                //West
                if (j_neg){
                    for (int k=0; k<offset_index_shift; k++)
                        (*currentproduct)*=data[i][j-k];
                    compare_and_assign(maxproduct, currentproduct);
                }

                //Northwest
                if (i_neg && j_neg){
                    for (int k=0; k<offset_index_shift; k++)
                        (*currentproduct)*=data[i-k][j-k];
                    compare_and_assign(maxproduct, currentproduct);
                }
            }
        end = clock();

        double time_spent = (double)(end - begin) / CLOCKS_PER_SEC;

        printf("Iteration: %d, Time: %f, Max Product: %d\n", cycles+1,
               time_spent, *maxproduct);
    }

    free(currentproduct);
    free(maxproduct);

	return 0;
}