hdu 1548 A strange lift

        hdu 1548 A strange lift

        廣搜， 最短路徑也可以做。

#include <stdio.h>
#include <queue>
using namespace std;

#define MAX 205

struct node {
	int floor, k;
	int step;
};

int n, a, b;
node floors[MAX];
bool visited[MAX];
int flag;

int bfs() {
	queue<node> Q;
	node cur, next;
	int upFloor, downFloor;
	memset(visited, false, sizeof(visited));

	visited[a] = true;
	Q.push(floors[a]);

	while (!Q.empty()) {
		cur = Q.front();
		Q.pop();

		upFloor = cur.floor + cur.k;
		downFloor = cur.floor - cur.k;
		if (upFloor == b) {
			return floors[cur.floor].step + 1;
		} else if (downFloor == b) {
			return floors[cur.floor].step + 1;
		}

		if (upFloor <= n && !visited[upFloor]) {
			visited[upFloor] = true;
			floors[upFloor].step = cur.step + 1;
			Q.push(floors[upFloor]);
		}

		if (downFloor > 0 && !visited[downFloor]) {
			visited[downFloor] = true;
			floors[downFloor].step = cur.step + 1;
			Q.push(floors[downFloor]);
		}
	}

	return -1;
}

int main() {
	int i;
	int ans;

	while (scanf("%d", &n) != EOF && n) {
		scanf("%d%d", &a, &b);

		for (i = 1; i <= n; i++) {
			floors[i].floor = i;
			floors[i].step = 0;
			scanf("%d", &floors[i].k);
		}

		if (a == b) {
			printf("0\n");
		} else {
			ans = bfs();
			printf("%d\n", ans);
		}
	}

	return 0;
}