C language to achieve 2048 small game direction merging logic

void up(void)// Up 
{
	for(int y=0; y<4; y++)
	{
		int end = 0;
		for(int x=1; x<4; x++)
		{
			for(int i=x; i>end; i--)
			{
				if(view[i][y])
				{
					if(0 == view[i-1][y])
					{
						//  Move 
						view[i-1][y] = view[i][y];
						view[i][y] = 0;
						flag = true;
					}
					else if(view[i][y] == view[i-1][y])
					{
						//	 Merge 
						view[i-1][y] *= 2;
						view[i][y] = 0;
						end = i;
						flag = true;
					}
				}
			}
		}
	}
}

void down(void)
{
    for(int y=0; y<4; y++)
    {
        int end = 4;
        for(int x=3; x>0; x--)
        {
            for(int i=x; i<end; i++)
            {
                if(view[i-1][y])
                {
                    if(0 == view[i][y])
                    {
                        //  Move 
                        view[i][y] = view[i-1][y];
                        view[i-1][y] = 0;
                        flag = true;
                    }
                    else if(view[i-1][y] == view[i][y])
                    {
                        //   Merge 
                        view[i][y] *= 2;
                        view[i-1][y] = 0;
                        end = i-1;
                        score +=view[i][y];
                        flag = true;
                    }
                }
            }
        }
    }
}

void right(void)
{
    for(int x=0; x<4; x++)
    {
        int end = 4;
        for(int y=3; y>0; y--)
        {
            for(int i=y; i<end; i++)
            {
                if(view[x][i-1])
                {
                    if(0 == view[x][i])
                    {
                        //  Move 
                        view[x][i] = view[x][i-1];
                        view[x][i-1] = 0;
                        flag = true;
                    }
                    else if(view[x][i-1] == view[x][i])
                    {
                        //   Merge 
                        view[x][i] *= 2;
                        view[x][i-1] = 0;
                        end = i-1;
                        score +=view[x][i];
                        flag = true;
                    }
                }
            }
        }
    }
}

void left(void)
{
    for(int x=0; x<4; x++)
    {
        int end = 0;
        for(int y=1; y<4; y++)
        {
            for(int i=y; i>end; i--)
            {
                if(view[x][i])
                {
                    if(0 == view[x][i-1])
                    {
                        //  Move 
                        view[x][i-1] = view[x][i];
                        view[x][i] = 0;
                        flag = true;
                    }
                    else if(view[x][i] == view[x][i-1])
                    {
                        //   Merge 
                        view[x][i-1] *= 2;
                        view[x][i] = 0;
                        end = i;
                        score +=view[x][i-1];
                        flag = true;
                    }
                }
            }
        }
    }
}