dailyprogrammer 261 easy

magic.c

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

int verify(int *square, int side) {
    int i, j, sum, target;

    // diagonals
    target = 0;
    for (i = 0; i < side; i++)
        target += square[i*side + i];
    sum = 0;
    for (i = 0; i < side; i++)
        sum += square[i*side + side-i-1];
    if (sum != target)
        return 0;

    // horizontals
    for (i = 0; i < side; i++) {
        sum = 0;
        for (j = 0; j < side; j++)
            sum += square[i*side + j];
        if (sum != target)
            return 0;
    }

    // verticals
    for (i = 0; i < side; i++) {
        sum = 0;
        for (j = 0; j < side; j++)
            sum += square[j*side + i];
        if (sum != target)
            return 0;
    }

    return 1;
}

int can_complete(int *rect, int side) {
    int i, j, sum, target;

    // horizontal on row 0
    target = 0;
    for (i = 0; i < side; i++)
        target += rect[i];

    // horizontals from rows 1 upto side-1 (excluding)
    for (i = 0; i < side-1; i++) {
        sum = 0;
        for (j = 0; j < side; j++)
            sum += rect[i*side + j];
        if (sum != target)
            return 0;
    }

    int *last_row = malloc(side * sizeof(int));

    int last_row_sum = 0;
    for (i = 0; i < side; i++) {
        sum = 0;
        for (j = 0; j < side-1; j++)
            sum += rect[j*side + i];
        if (target < sum)
            return 0;
        last_row[i] = target - sum;
        last_row_sum += last_row[i];
    }

    if (last_row_sum != target)
        return 1;

    // finally, check both diagonals
    sum = 0;
    for (i = 0; i < side-1; i++)
        sum += rect[i*side + side-i-1];
    if (sum + last_row[0] != target)
        return 0;
    sum = 0;
    for (i = 0; i < side-1; i++)
        sum += rect[i*side + i];
    return target == (sum + last_row[side-1]);
}

int main() {
    int verify_tests[4][9] = {{8, 1, 6, 3, 5, 7, 4, 9, 2},
                              {2, 7, 6, 9, 5, 1, 4, 3, 8},
                              {3, 5, 7, 8, 1, 6, 4, 9, 2},
                              {8, 1, 6, 7, 5, 3, 4, 9, 2}};
    int i;
    for (i = 0; i < 4; i++)
        printf("%d ", verify(verify_tests[i], 3));

    int cc_tests[2][6] = {{8, 1, 6, 3, 5, 7},
                          {3, 5, 7, 8, 1, 6}};

    for (i = 0; i < 2; i++)
        printf("%d ", can_complete(cc_tests[i], 3));

    return 0;
}