test.c

typedef struct {
    int x;
    int y;
} Point;

typedef struct {
    Point s;
    Point e;
} Line;

Point LineLineIntersect(int x1, int y1, //Line 1 start
    int x2, int y2, //Line 1 end
    int x3, int y3, //Line 2 start
    int x4, int y4 //Line 2 end
    )
{
    Point result;

int detL1 = 0;
int detL2 = 0;
int x1mx2 = 0;
int x3mx4 = 0;
int y1my2 = 0;
int y3my4 = 0;
int xnom = 0;
int ynom = 0;
int denom = 0;

    detL1 = x1 * y2 - y1 * x2;
    detL2 = x3 * y4 - y3 * x4;
    x1mx2 = x1 - x2;
    x3mx4 = x3 - x4;
    y1my2 = y1 - y2;
    y3my4 = y3 - y4;
 
    xnom = detL1 * x3mx4 - x1mx2 * detL2;
    ynom = detL1 * y3my4 - y1my2 * detL2;
    denom = x1mx2 * y3my4 - y1my2 * x3mx4;
    if (denom == 0) {
        // Lines don't seem to cross
        result.x = 99999;
        result.y = 99999;
        return result;
    }

    result.x = xnom / denom;
    result.y = ynom / denom;

    return result;
}

Point mpc_main(Line INPUT_A, Line INPUT_B) {
    return LineLineIntersect(INPUT_A.s.x, INPUT_A.s.y, INPUT_A.e.x, INPUT_A.e.y,
                             INPUT_B.s.x, INPUT_B.s.y, INPUT_B.e.x, INPUT_B.e.y);
}