C,得分2.397x10 ^ 38
男人花了很长时间来做,很可能是由于我选择的语言。我使算法相当早就开始工作,但是在内存分配方面遇到了很多问题(由于堆栈溢出,泄漏量很大,无法递归释放东西)。
仍然!它在每个测试用例上都胜过其他条目,甚至可能很多时候都是最优方案,或者接近最优方案。
无论如何,这是代码:
#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
#include <string.h>
#define WHITE 'W'
#define BLACK 'B'
#define RED 'R'
typedef struct image {
int w, h;
char* buf;
} image;
typedef struct point {
int x, y;
struct point *next;
struct point *parent;
} point;
typedef struct shape {
point* first_point;
point* last_point;
struct shape* next_shape;
} shape;
typedef struct storage {
point* points;
size_t points_size;
size_t points_index;
shape* shapes;
size_t shapes_size;
size_t shapes_index;
} storage;
char getpx(image* img, int x, int y) {
if (0>x || x>=img->w || 0>y || y>=img->h) {
return WHITE;
} else {
return img->buf[y*img->w+x];
}
}
storage* create_storage(int w, int h) {
storage* ps = (storage*)malloc(sizeof(storage));
ps->points_size = 8*w*h;
ps->points = (point*)calloc(ps->points_size, sizeof(point));
ps->points_index = 0;
ps->shapes_size = 2*w*h;
ps->shapes = (shape*)calloc(ps->shapes_size, sizeof(shape));
ps->shapes_index = 0;
return ps;
}
void free_storage(storage* ps) {
if (ps != NULL) {
if (ps->points != NULL) {
free(ps->points);
ps->points = NULL;
}
if (ps->shapes != NULL) {
free(ps->shapes);
ps->shapes = NULL;
}
free(ps);
}
}
point* alloc_point(storage* ps) {
if (ps->points_index == ps->points_size) {
printf("WHOAH THERE BUDDY SLOW DOWN\n");
/*// double the size of the buffer
point* new_buffer = (point*)malloc(ps->points_size*2*sizeof(point));
// need to change all existing pointers to point to new buffer
long long int pointer_offset = (long long int)new_buffer - (long long int)ps->points;
for (size_t i=0; i<ps->points_index; i++) {
new_buffer[i] = ps->points[i];
if (new_buffer[i].next != NULL) {
new_buffer[i].next += pointer_offset;
}
if (new_buffer[i].parent != NULL) {
new_buffer[i].parent += pointer_offset;
}
}
for(size_t i=0; i<ps->shapes_index; i++) {
if (ps->shapes[i].first_point != NULL) {
ps->shapes[i].first_point += pointer_offset;
}
if (ps->shapes[i].last_point != NULL) {
ps->shapes[i].last_point += pointer_offset;
}
}
free(ps->points);
ps->points = new_buffer;
ps->points_size = ps->points_size * 2;*/
}
point* out = &(ps->points[ps->points_index]);
ps->points_index += 1;
return out;
}
shape* alloc_shape(storage* ps) {
/*if (ps->shapes_index == ps->shapes_size) {
// double the size of the buffer
shape* new_buffer = (shape*)malloc(ps->shapes_size*2*sizeof(shape));
long long int pointer_offset = (long long int)new_buffer - (long long int)ps->shapes;
for (size_t i=0; i<ps->shapes_index; i++) {
new_buffer[i] = ps->shapes[i];
if (new_buffer[i].next_shape != NULL) {
new_buffer[i].next_shape += pointer_offset;
}
}
free(ps->shapes);
ps->shapes = new_buffer;
ps->shapes_size = ps->shapes_size * 2;
}*/
shape* out = &(ps->shapes[ps->shapes_index]);
ps->shapes_index += 1;
return out;
}
shape floodfill_shape(image* img, storage* ps, int x, int y, char* buf) {
// not using point allocator for exploration stack b/c that will overflow it
point* stack = (point*)malloc(sizeof(point));
stack->x = x;
stack->y = y;
stack->next = NULL;
stack->parent = NULL;
point* explored = NULL;
point* first_explored;
point* next_explored;
while (stack != NULL) {
int sx = stack->x;
int sy = stack->y;
point* prev_head = stack;
stack = stack->next;
free(prev_head);
buf[sx+sy*img->w] = 1; // mark as explored
// add point to shape
next_explored = alloc_point(ps);
next_explored->x = sx;
next_explored->y = sy;
next_explored->next = NULL;
next_explored->parent = NULL;
if (explored != NULL) {
explored->next = next_explored;
} else {
first_explored = next_explored;
}
explored = next_explored;
for (int dy=-1; dy<2; dy++) {
for (int dx=-1; dx<2; dx++) {
if (dy != 0 || dx != 0) {
int nx = sx+dx;
int ny = sy+dy;
if (getpx(img, nx, ny) == WHITE || buf[nx+ny*img->w]) {
// skip adding point to fringe
} else {
// push point to top of stack
point* new_point = (point*)malloc(sizeof(point));
new_point->x = nx;
new_point->y = ny;
new_point->next = stack;
new_point->parent = NULL;
stack = new_point;
}
}
}
}
}
/*if (getpx(img, x, y) == WHITE || buf[x+y*img->w]) {
return (shape){NULL, NULL, NULL};
} else {
buf[x+y*img->w] = 1;
shape e = floodfill_shape(img, ps, x+1, y, buf);
shape ne = floodfill_shape(img, ps, x+1, y+1, buf);
shape n = floodfill_shape(img, ps, x, y+1, buf);
shape nw = floodfill_shape(img, ps, x-1, y+1, buf);
shape w = floodfill_shape(img, ps, x-1, y, buf);
shape sw = floodfill_shape(img, ps, x-1, y-1, buf);
shape s = floodfill_shape(img, ps, x, y-1, buf);
shape se = floodfill_shape(img, ps, x+1, y-1, buf);
point *p = alloc_point(ps);
p->x = x;
p->y = y;
p->next = NULL;
p->parent = NULL;
shape o = (shape){p, p, NULL};
if (e.first_point != NULL) {
o.last_point->next = e.first_point;
o.last_point = e.last_point;
}
if (ne.first_point != NULL) {
o.last_point->next = ne.first_point;
o.last_point = ne.last_point;
}
if (n.first_point != NULL) {
o.last_point->next = n.first_point;
o.last_point = n.last_point;
}
if (nw.first_point != NULL) {
o.last_point->next = nw.first_point;
o.last_point = nw.last_point;
}
if (w.first_point != NULL) {
o.last_point->next = w.first_point;
o.last_point = w.last_point;
}
if (sw.first_point != NULL) {
o.last_point->next = sw.first_point;
o.last_point = sw.last_point;
}
if (s.first_point != NULL) {
o.last_point->next = s.first_point;
o.last_point = s.last_point;
}
if (se.first_point != NULL) {
o.last_point->next = se.first_point;
o.last_point = se.last_point;
}
return o;
}*/
shape out = {first_explored, explored, NULL};
return out;
}
shape* create_shapes(image* img, storage* ps) {
char* added_buffer = (char*)calloc(img->w*img->h, sizeof(char));
shape* first_shape = NULL;
shape* last_shape = NULL;
int num_shapes = 0;
for (int y=0; y<img->h; y++) {
for (int x=0; x<img->w; x++) {
if (getpx(img, x, y) != WHITE && !(added_buffer[x+y*img->w])) {
shape* alloced_shape = alloc_shape(ps);
*alloced_shape = floodfill_shape(img, ps, x, y, added_buffer);
if (first_shape == NULL) {
first_shape = alloced_shape;
last_shape = alloced_shape;
} else if (last_shape != NULL) {
last_shape->next_shape = alloced_shape;
last_shape = alloced_shape;
}
num_shapes++;
}
}
}
free(added_buffer);
return first_shape;
}
void populate_buf(image* img, shape* s, char* buf) {
point* p = s->first_point;
while (p != NULL) {
buf[p->x+p->y*img->w] = 1;
p = p->next;
}
}
bool expand_frontier(image* img, storage* ps, shape* prev_frontier, shape* next_frontier, char* buf) {
point* p = prev_frontier->first_point;
point* n = NULL;
bool found = false;
size_t starting_points_index = ps->points_index;
while (p != NULL) {
for (int dy=-1; dy<2; dy++) {
for (int dx=-1; dx<2; dx++) {
if (dy != 0 || dx != 0) {
int nx = p->x+dx;
int ny = p->y+dy;
if ((0<=nx && nx<img->w && 0<=ny && ny<img->h) // in bounds
&& !buf[nx+ny*img->w]) { // not searched yet
buf[nx+ny*img->w] = 1;
if (getpx(img, nx, ny) != WHITE) {
// found a new shape!
ps->points_index = starting_points_index;
n = alloc_point(ps);
n->x = nx;
n->y = ny;
n->next = NULL;
n->parent = p;
found = true;
goto __expand_frontier_fullbreak;
} else {
// need to search more
point* f = alloc_point(ps);
f->x = nx;
f->y = ny;
f->next = n;
f->parent = p;
n = f;
}
}
}
}}
p = p->next;
}
__expand_frontier_fullbreak:
p = NULL;
point* last_n = n;
while (last_n->next != NULL) {
last_n = last_n->next;
}
next_frontier->first_point = n;
next_frontier->last_point = last_n;
return found;
}
void color_from_frontier(image* img, point* frontier_point) {
point* p = frontier_point->parent;
while (p->parent != NULL) { // if everything else is right,
// a frontier point should come in a chain of at least 3
// (f point (B) -> point to color (W) -> point in shape (B) -> NULL)
img->buf[p->x+p->y*img->w] = RED;
p = p->parent;
}
}
int main(int argc, char** argv) {
if (argc < 3) {
printf("Error: first argument must be filename to load, second argument filename to save to.\n");
return 1;
}
char* fname = argv[1];
FILE* fp = fopen(fname, "r");
if (fp == NULL) {
printf("Error opening file \"%s\"\n", fname);
return 1;
}
int w, h;
w = 0;
h = 0;
fscanf(fp, "%d %d\n", &w, &h);
if (w==0 || h==0) {
printf("Error: invalid width/height specified\n");
return 1;
}
char* buf = (char*)malloc(sizeof(char)*w*h+1);
fgets(buf, w*h+1, fp);
fclose(fp);
image img = (image){w, h, buf};
int nshapes = 0;
storage* ps = create_storage(w, h);
while (nshapes != 1) {
// main loop, do processing step until one shape left
ps->points_index = 0;
ps->shapes_index = 0;
shape* head = create_shapes(&img, ps);
nshapes = 0;
shape* pt = head;
while (pt != NULL) {
pt = pt->next_shape;
nshapes++;
}
if (nshapes % 1024 == 0) {
printf("shapes left: %d\n", nshapes);
}
if (nshapes == 1) {
goto __main_task_complete;
}
shape* frontier = alloc_shape(ps);
// making a copy so we can safely free later
point* p = head->first_point;
point* ffp = NULL;
point* flp = NULL;
while (p != NULL) {
if (ffp == NULL) {
ffp = alloc_point(ps);
ffp->x = p->x;
ffp->y = p->y;
ffp->next = NULL;
ffp->parent = NULL;
flp = ffp;
} else {
point* fnp = alloc_point(ps);
fnp->x = p->x;
fnp->y = p->y;
fnp->next = NULL;
fnp->parent = NULL;
flp->next = fnp;
flp = fnp;
}
p = p->next;
}
frontier->first_point = ffp;
frontier->last_point = flp;
frontier->next_shape = NULL;
char* visited_buf = (char*)calloc(img.w*img.h+1, sizeof(char));
populate_buf(&img, frontier, visited_buf);
shape* new_frontier = alloc_shape(ps);
new_frontier->first_point = NULL;
new_frontier->last_point = NULL;
new_frontier->next_shape = NULL;
while (!expand_frontier(&img, ps, frontier, new_frontier, visited_buf)) {
frontier->first_point = new_frontier->first_point;
frontier->last_point = new_frontier->last_point;
new_frontier->next_shape = frontier;
}
free(visited_buf);
color_from_frontier(&img, new_frontier->first_point);
__main_task_complete:
img = img;
}
free_storage(ps);
char* outfname = argv[2];
fp = fopen(outfname, "w");
if (fp == NULL) {
printf("Error opening file \"%s\"\n", outfname);
return 1;
}
fprintf(fp, "%d %d\n", img.w, img.h);
fprintf(fp, "%s", img.buf);
free(img.buf);
fclose(fp);
return 0;
}
经过测试:Arch Linux,GCC 9.1.0, -O3
该代码在我称为“ cppm”的自定义文件中接受输入/输出(因为它就像经典PPM格式的压缩版本一样)。下面是要转换成/从中转换的python脚本:
from PIL import Image
BLACK='B'
WHITE='W'
RED ='R'
def image_to_cppm(infname, outfname):
outfile = open(outfname, 'w')
im = Image.open(infname)
w, h = im.width, im.height
outfile.write(f"{w} {h}\n")
for y in range(h):
for x in range(w):
r, g, b, *_ = im.getpixel((x, y))
if r==0 and g==0 and b==0:
outfile.write(BLACK)
elif g==0 and b==0:
outfile.write(RED)
else:
outfile.write(WHITE)
outfile.write("\n")
outfile.close()
im.close()
def cppm_to_image(infname, outfname):
infile = open(infname, 'r')
w, h = infile.readline().split(" ")
w, h = int(w), int(h)
im = Image.new('RGB', (w, h), color=(255, 255, 255))
for y in range(h):
for x in range(w):
c = infile.read(1)
if c==BLACK:
im.putpixel((x,y), (0, 0, 0))
elif c==RED:
im.putpixel((x,y), (255, 0, 0))
infile.close()
im.save(outfname)
im.close()
if __name__ == "__main__":
import sys
if len(sys.argv) < 3:
print("Error: must provide 2 files to convert, first is from, second is to")
infname = sys.argv[1]
outfname = sys.argv[2]
if not infname.endswith("cppm") and outfname.endswith("cppm"):
image_to_cppm(infname, outfname)
elif infname.endswith("cppm") and not outfname.endswith("cppm"):
cppm_to_image(infname, outfname)
else:
print("didn't do anything, exactly one file must end with .cppm")
算法说明
该算法的工作原理是从找到图像中所有连接的形状(包括红色像素)开始。然后,它获取第一个像素并一次扩展其边界一个像素,直到遇到另一种形状为止。然后,它为从触摸到原始形状的所有像素着色(使用在跟踪过程中创建的链接列表)。最后,它重复该过程,找到所有创建的新形状,直到只剩下一个形状。
图片库
测试用例1,183像素
测试用例2,140像素
测试用例3,244像素
测试用例4,42像素
测试用例5,622像素
测试用例6,1像素
测试用例7,104像素
测试用例8,2286像素
测试用例9,22像素
测试案例10,31581像素
测试用例11,21421像素
测试用例12,5465像素
测试用例13,4679像素
测试用例14,7362像素