I've been trying to program a tile based game, and I'm stuck at the collision detection.

Here is my code (not the best ^^):

void checkTile(Character *c, int **map)
{
     int x1,x2,y1,y2;

     /* Character position in the map */
     c->upY     = (c->y)                / TILE_SIZE; // Top left corner
     c->downY   = (c->y + c->h)         / TILE_SIZE; // Bottom left corner
     c->leftX   = (c->x)                / TILE_SIZE; // Top right corner
     c->rightX  = (c->x + c->w)         / TILE_SIZE; // Bottom right corner

     x1         = (c->x + 10)           / TILE_SIZE; // 10px from left side point
     x2         = (c->x + c->w - 10)    / TILE_SIZE; // 10px from right side point
     y1         = (c->y + 10)           / TILE_SIZE; // 10px from top side point
     y2         = (c->y + c->h - 10)    / TILE_SIZE; // 10px from bottom side point


     /* Top */
     if (map[c->upY][x1] > 2 || map[c->upY][x2] > 2)
         c->topCollision = 1;
     else c->topCollision = 0;

     /* Bottom */
     if ((map[c->downY][x1] > 2 || map[c->downY][x2] > 2))
         c->downCollision = 1;
     else c->downCollision = 0;

     /* Left */
     if (map[y1][c->leftX] > 2 || map[y2][c->leftX] > 2)
         c->leftCollision = 1;
     else c->leftCollision = 0;

     /* Right */
     if (map[y1][c->rightX] > 2 || map[y2][c->rightX] > 2)
         c->rightCollision = 1;
     else c->rightCollision = 0;
 }

That calculates 8 collision points

My moving function is like that:

 void movePlayer(Character *c, int **map)
 {
    if ((c->dirX == LEFT && !c->leftCollision) || (c->dirX == RIGHT && !c->rightCollision))
    c->x += c->vx;

    if ((c->dirY == UP && !c->topCollision) || (c->dirY == DOWN && !c->downCollision))
        c->y += c->vy;

    checkPosition(c, map);
 }

and the checkPosition:

void checkPosition(Character *c, int **map)
{
checkTile(c, map);

if (c->downCollision) {
    if (c->state != JUMPING) {
        c->vy = 0;
        c->y = (c->downY * TILE_SIZE - c->h);
    }
}

if (c->leftCollision) {
    c->vx = 0;
    c->x = (c->leftX) * TILE_SIZE + TILE_SIZE;
}

if (c->rightCollision) {
    c->vx = 0;
    c->x = c->rightX * TILE_SIZE - c->w;
}
}

This works, but sometimes, when the player is landing on ground, right and left collision points become equal to 1. So it's as if there were collision coming from left or right.

Does anyone know why this is doing this?