cv4

//1a)
#include <stdio.h>

int main()
{
    int x = 0;
    scanf("%d", &x);
    printf(x < 0 ? "zaporne\n" : "nezaporne\n" );

    return 0;
}
//1b)
#include <stdio.h>

int main()
{
    int x = 0;
    scanf("%d", &x);
    printf(x < 0 ? "zaporne\n" : x == 0 ? "nula\n" : "kladne\n" );

    return 0;
}
//1c
#include <stdio.h>
#include <math.h>

int main()
{
    int a = 0,b = 0;
    scanf("%d %d", &a, &b);
    printf("%d\n", a>b?a:b );
    printf("%d\n", (int)(a+b+fabs(a-b))/2);

    return 0;
}
//2
#include <stdio.h>

int main()
{
    int a = 0;
    scanf("%d", &a);
    if (a < 1 || a > 7)
    {
        printf("bad input\n");
        return 0;
    }
    switch (a)
    {
        case 1:
            printf("pondeli\n");
            break;
        case 2:
            printf("utery\n");
            break;
        case 3:
            printf("streda\n");
            break;
        case 4:
            printf("ctvrtek\n");
            break;
        case 5:
            printf("patek\n");
            break;
        case 6:
            printf("sobota\n");
            break;
        case 7:
            printf("nedele\n");
            break;

    }

    return 0;
}
//3
#include <stdio.h>

int main()
{
    int a = 0, b = 0, c = 0;

    b = 1;
    c = 2;
    a = ++b + c++; /* a = 4 */
    printf("b = 1\nc = 2\na = ++b + c++\na = %d\n\n", a);

    b = 1;
    c = b += 2;
    a = b / c; /* 3 / 3 */
    printf("b = 1\nc = b += 2\na = b / c\na = %d %d\n\n", a, b % c);

    return 0;
}
//4
#include <stdio.h>

int main()
{
    int r = 0;
    scanf("%d", &r);
    if (r < 0)
    {
        printf("bad input\n");
        return 0;
    }
    printf( (r % 4 == 0 && (r % 100 != 0 ||  r % 400 == 0)) ? "prestupny" : "neni prestupny");

    return 0;
}
//5
#include <stdio.h>
#include <math.h>

int main()
{
    int a = 0, b = 0, c = 0;
    scanf("%d %d %d", &a, &b, &c);
    if (a < 0 || b < 0 || c < 0 || a+b < c || b+c < a || c+a < b)
    {
        printf("nelze sestrojit\n");
        return 0;
    }
    printf("lze sestrojit\n");
    printf((a == b && b == c) ? "je rovnostranny\n" : "");
    printf((a == b || b == c || c == a) && !(a == b && b == c) ? "je rovnoramenny\n" : "");
    printf((sqrt(a*a+b*b) == c || sqrt(b*b+c*c) == a || sqrt(c*c+a*a) == b ) ?  "je pravouhly" : "");

    return 0;
}
//6
#include <stdio.h>
#include <math.h>

int main()
{
    int a = 0, b = 0, c = 0;
    double d = 0;
    printf("zadejte koeficinety  rovnice ax^2 + bx + c = 0 [a b c]\n");
    scanf("%d %d %d", &a, &b, &c);

    if (a == 0)
    {
        printf("linearni rovnice %dx + %d = 0\n", b, c);
        printf("x = %g\n", (double)-c/(double)b);
        return 0;
    }

    if (b == 0)
    {
        printf("kvadraticka rovnice bez linearniho clenu %dx^2 + %d = 0\n", a, c);
        if (c < 0)
            printf("x1,x2 = +-%g\n", sqrt((double)-c/(double)a));
        else
            printf("x1,x2 = +-%gi\n", sqrt((double)c/(double)a));
        return 0;
    }

    d = b*b - 4*a*c;
    if (d < 0)
        printf("x1 = %g + %gi, x2 = %g - %gi\n", (double)-b/(double)(2*a), sqrt(-d), (double)-b/(double)(2*a), sqrt(-d));
    else if (d == 0)
        printf("x1 = %g\n", (((double)-b))/(double)(2*a));
    else
        printf("x1 = %g, x2 = %g\n", (((double)-b)+sqrt(d))/(double)(2*a) , (((double)-b)-sqrt(d))/(double)(2*a));
    return 0;
}
Advanced
#include <stdio.h>

int main()
{
    int ax = 0, ay = 0, bx = 0, by = 0, cx = 0, cy = 0;
    printf("zadejte body primky p A a B a bod C\nA[x, y]:");
    scanf("%d %d", &ax, &ay);
    printf("B[x, y]:");
    scanf("%d %d", &bx, &by);
    printf("C[x, y]:");
    scanf("%d %d", &cx, &cy);

    /*
    A[ax, ay]
    C[bx, by]
    smerovy vektor u = AB = B-A = (bx-ax, by-ay)
    normalovy vektor n = (ay-by, bx-ax)
    x = ay - by;
    y = bx - ax;
    obecna rovnice primky (ay-by)x + (bx-ax)y + c = 0
    konstantu c ziskame dosazenim budo A do rovnice
    c = -( ax * (ay - by) + ay * (bx - ax) );
    (ay-by)x + (bx-ax)y + -(ax*(ay-by)+ay*(bx-ax)) = 0
    overeni zdali bod lezi na primce, dosadime za x a y

    */

    if (( cx * ( ay - by ) + cy * (bx - ax) ) == ( ax * (ay - by) + ay * (bx - ax) ))
        printf("Bod C lezi na primce\n");
    else
        printf("Bod C nelezi na primce\n");
    return 0;
}