0

我设置了一个递归洪水填充算法，由于（我认为）达到堆栈溢出/递归深度而导致段错误。我不想弄乱堆栈限制，创建这个特定算法的迭代版本超出了我的技能水平。所以，我只想让函数在这么多循环后停止，所以它只会安全地填充小区域。

我创建了一个测试程序来解决终止条件的实现，但是我注意到尽管完成了它的工作，该函数仍在运行。例如，在下面的代码中，让它运行 200,000 次可以正确填充窗口，但 300,000 也是如此，当我让它运行 400,000 次时，它会在 337,977 处安全地停止循环。所以我很困惑到底是什么让它在 337,977 处停止，以及如何让它在我用眼睛看到的洪水填充的实际结束时停止，循环次数不到 200,000 次。

#include <stdio.h>
#include <SDL2/SDL.h>
Uint32 myPixelColour(Uint32 *pixels, int x, int y, int windowWidth, int windowHeight)
{

    Uint32 thisPixelColour = 0;
    thisPixelColour = pixels[x + y * windowWidth];
    return thisPixelColour;
}

int mySameColour(Uint32 thisPixelColour, Uint32 thatPixelColour)
{
    return (thisPixelColour == thatPixelColour);
}

void myFill(Uint32 *pixels, int windowWidth, int windowHeight, int x, int y, Uint32 finColour, int *counter)
{
    if(!((x>=0) && (x<windowWidth) && (y>=0) && (y<windowHeight))) return;
    if(*counter == 400000) return;  /* 200000 fills the window, so does 300000 */
    printf("%d\n", *counter);
    *counter = *counter + 1;

    Uint32 ogColour = myPixelColour(pixels, x, y, windowWidth, windowHeight);
    if(mySameColour(ogColour, finColour)) return;
    pixels[x+y*windowWidth] = finColour;

    myFill(pixels, windowWidth, windowHeight, x, y+1, finColour, counter);
    myFill(pixels, windowWidth, windowHeight, x-1, y, finColour, counter);
    myFill(pixels, windowWidth, windowHeight, x, y-1, finColour, counter);
    myFill(pixels, windowWidth, windowHeight, x+1, y, finColour, counter);
}

int main(void)
{
    const int windowWidth = 400;
    const int windowHeight = 212;
    int counter;
    counter = 1;

    SDL_Window *window = SDL_CreateWindow("WindowTitle", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED, windowWidth, windowHeight, SDL_WINDOW_SHOWN);
    SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, 0);
    SDL_Texture *texture = SDL_CreateTexture(renderer, SDL_PIXELFORMAT_ARGB8888, SDL_TEXTUREACCESS_STATIC, windowWidth, windowHeight);

    Uint32 *pixels = NULL;
    pixels = (Uint32 *) malloc (sizeof(Uint32)*(Uint32)windowWidth*(Uint32)windowHeight);
    memset(pixels, 255, (Uint32)windowWidth*(Uint32)windowHeight*sizeof(Uint32));

    Uint32 finColour = 0x99FFCC;

    SDL_Point mouse_position;
    int success = 1;
    while(success)
    {
        SDL_Event userAction;

        SDL_GetMouseState(&mouse_position.x, &mouse_position.y);

        SDL_UpdateTexture(texture, NULL, pixels, (int)((Uint32)windowWidth * sizeof(Uint32)));

        while(SDL_PollEvent(&userAction))
        {
            switch(userAction.type)
            {
                case SDL_QUIT: success = 0; break;
                case SDL_KEYDOWN:
                    if(userAction.key.keysym.sym == SDLK_f)
                    {
                        myFill(pixels, windowWidth, windowHeight, 1, 1, finColour, &counter);
                    }
                    break;
            }
        }

        SDL_RenderClear(renderer);
        SDL_RenderCopy(renderer, texture, NULL, NULL);
        SDL_RenderPresent(renderer);
    }
    free(pixels);
    SDL_DestroyTexture(texture);
    SDL_DestroyRenderer(renderer);
    SDL_DestroyWindow(window);
    return 0;
}
4

0 回答 0