黑白图像显示栈版

《算法竞赛入门经典》中的例子，书中只提供了递归栈的版本，让读者试着改成显示栈的。不过我改了半天也没改成，想起《Linux C编程一站式学习》中有深度优先搜索一节过去就没看懂，于是就参考了那一节，这次不仅看懂了，显示栈的版本也写成了，看来黑白图像和走迷宫这两个例子真是很适合结合起来以循序渐进地学习DFS啊！

#include <stdio.h>#include <string.h>#define N 100typedef struct { int x, y; } Point;Point stack[N];int top = 0;char mat[N][N], vis[N][N];void push(int x, int y){stack[top].x = x;stack[top].y = y;++top;vis[x][y] = 1;}Point pop(void){return stack[--top];}int is_empty(void){return top == 0;}int dfs(int x, int y){Point p;if (!mat[x][y] || vis[x][y])return 0;push(x, y);while (!is_empty()) {p = pop();if (mat[p.x+1][p.y] && !vis[p.x+1][p.y])push(p.x+1, p.y);if (mat[p.x+1][p.y+1] && !vis[p.x+1][p.y+1])push(p.x+1, p.y+1);if (mat[p.x-1][p.y] && !vis[p.x-1][p.y])push(p.x-1, p.y);if (mat[p.x-1][p.y-1] && !vis[p.x-1][p.y-1])push(p.x-1, p.y-1);if (mat[p.x][p.y+1] && !vis[p.x][p.y+1])push(p.x, p.y+1);if (mat[p.x][p.y-1] && !vis[p.x][p.y-1])push(p.x, p.y-1);if (mat[p.x+1][p.y-1] && !vis[p.x+1][p.y-1])push(p.x+1, p.y-1);if (mat[p.x-1][p.y+1] && !vis[p.x-1][p.y+1])push(p.x-1, p.y+1);}return 1;}int main(void){int n, x, y, count = 0;char c;scanf("%d", &n);memset(mat, 0, sizeof(mat));memset(vis, 0, sizeof(vis));for (x = 0; x < n; ++x)for (y = 0; y < n; ++y) {scanf(" %c", &c);mat[x+1][y+1] = c-'0';}for (x = 1; x <= n; ++x)for (y = 1; y <= n; ++y)if (dfs(x, y))count++;printf("%d\n", count);return 0;}