HDU 5012 Dice

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有一个六面骰子，有四种翻面方法，求由原状态到目标状态需要翻的最小次数

BFS:

#include <stdio.h>#include <string.h>#define MAXN 1024struct Dice {int a[6];int n;static int dir[4][6];int value () {int sum = 0;for (int i = 0; i < 6; i ++) {sum *= 10;sum += a[i];}return sum;}Dice rotation(int k) {Dice dice;for (int i = 0; i < 6; i ++)dice.a[i] = a[dir[k][i]];return dice;}} queue[MAXN];int Dice :: dir[4][6] = {{3, 2, 0, 1, 4, 5}, {2, 3, 1, 0, 4, 5}, {5, 4, 2, 3, 0, 1}, {4, 5, 2, 3, 1, 0}};int values[MAXN], num;int aim[6];bool judge (int k) {for (int i = 0; i < num; i ++)if (values[i] == k)return false;values[num ++] = k;return true;}int BFS () {int front = 0, rear = 1;queue[0].n = 0;while (front < rear) {Dice& dice = queue[front ++];if (memcmp(dice.a, aim, sizeof(aim)) == 0)return dice.n;for (int i = 0; i < 4; i ++) {queue[rear] = dice.rotation(i);if (judge(queue[rear].value())) {queue[rear ++].n = dice.n + 1;}}}return -1;}int main() {//freopen ("in.txt", "r", stdin);while (~scanf ("%d", &queue[0].a[0])) {num = 0;for (int i = 1; i < 6; i ++)scanf ("%d", &queue[0].a[i]);for (int i = 0; i < 6; i ++) {scanf ("%d", &aim[i]);}printf ("%d\n", BFS());}return 0;}

DFS(由于需要判断骰子可以翻到所有情况（存在大量重复）来确定最小次数，故该方法效率太低，超时):

#include <stdio.h>#include <string.h>#define MAXN 1024typedef int Dice[6];int dir[4][6] = {{3, 2, 0, 1, 4, 5}, {2, 3, 1, 0, 4, 5}, {5, 4, 2, 3, 0, 1}, {4, 5, 2, 3, 1, 0}};int values[MAXN], sum;Dice begin, aim;bool judge (int k, int num) {for (int i = 0; i < num; i ++)if (values[i] == k)return false;return true;}int value (Dice& a) {int sum = 0;for (int i = 0; i < 6; i ++) {sum *= 10;sum += a[i];}return sum;}void DFS (Dice& dice, int cur) {if (memcmp(dice, aim, sizeof(aim)) == 0 && (cur < sum || sum == -1)) {sum = cur;return;}Dice ndice;int k;for (int i = 0; i < 4; i ++) {for (int j = 0; j < 6; j ++)ndice[j] = dice[dir[i][j]];k = value(ndice);if (judge(k, cur)) {values[cur] = k;DFS(ndice, cur + 1);}}}int main() {//freopen ("in.txt", "r", stdin);while (~scanf ("%d", &begin[0])) {sum = -1;for (int i = 1; i < 6; i ++)scanf ("%d", &begin[i]);for (int i = 0; i < 6; i ++) {scanf ("%d", &aim[i]);}DFS(begin, 0);printf ("%d\n", sum);}return 0;}

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