uva 439 - Knight Moves

先研究下国际象棋中马是怎么走的，然后bfs就哦了。

 

#include<stdio.h>
#include<string.h>
#include<stdlib.h>

int map[10][10];

typedef struct Point {
	int x;
	int y;
	int dis;
} Point;

typedef Point* Ptr;

Point queue[5000];

int dir[8][2] = { { -2, 1 }, { -2, -1 }, { -1, 2 }, { 1, 2 }, { -1, -2 }, { 1,
		-2 }, { 2, 1 }, { 2, -1 } };

int bfs(Point from, Point to) {
	if (from.x == to.x && from.y == to.y)
		return 0;

	int front = 0;
	int rear = 1;
	queue[0].x = from.x;
	queue[0].y = from.y;
	queue[0].dis = from.dis;
	while (front < rear) {
		Ptr p = &queue[front++];
		map[p->x][p->y] = 1;
		if (p->x == to.x && p->y == to.y)
			return p->dis;
		int k;
		int newX, newY;
		for (k = 0; k < 8; k++) {
			newX = p->x + dir[k][0];
			newY = p->y + dir[k][1];
			if (newX >= 1 && newX <= 8 && newY >= 1 && newY <= 8
					&& !map[newX][newY]) {
				queue[rear].x = newX;
				queue[rear].y = newY;
				queue[rear].dis = p->dis + 1;
				rear++;
			}
		}
	}
	return -1;
}

int main() {
	char start[5];
	char end[5];
	while (scanf("%s%s", start, end) != EOF) {
		memset(map, 0, sizeof(map));
		Point from, to;
		from.x = start[0] - 'a' + 1;
		from.y = start[1] - '0';
		from.dis = 0;
		to.x = end[0] - 'a' + 1;
		to.y = end[1] - '0';
		to.dis = -1;
		printf("To get from %s to %s takes %d knight moves.\n", start, end,
				bfs(from, to));
	}
	return 0;
}