poj2286 唯美的IDA*（80行）

ida*果然比a*强太多了，少了hash判重和堆维护，是估价函数和DFS的完美结合啊！

嗯，主要是DFS函数中第二行的那个强剪枝太给力了！IDA*的灵魂啊！

基本的架构就是如此了，可以任意套。

//poj2286
#include <iostream>
#include <cmath>
using namespace std;
const int b[5][8] = { 7,8,9,12,13,16,17,18,
                      1,3,7,12,16,21,23,0,
                      2,4,9,13,18,22,24,0,
                      11,10,9,8,7,6,5,0,
                      20,19,18,17,16,15,14,0};
const int c[9] = {0,1,2,3,4,6,5,8,7};
int a[25],stk[1010],bound,x,final;
bool ans;
int h(int *a) {
    int tmp[3]={0,0,0};
    for (int i=0;i<8;i++)
        tmp[a[b[0][i]]-1]++;
    return 8-max(max(tmp[0],tmp[1]),tmp[2]);
}
void trans(int *a,int p) {
     if (p<=4) {
               int tmp = a[b[p][0]];
               for (int i=0;i<6;i++)
                   a[b[p][i]]=a[b[p][i+1]];
               a[b[p][6]]=tmp;
     } else {
               p-=4;
               int tmp = a[b[p][6]];
               for (int i=6;i>0;i--)
                   a[b[p][i]]=a[b[p][i-1]];
               a[b[p][0]]=tmp;
     }
}
int dfs(int *a,int dep,int pre_move) {
    int hv = h(a);
    if (hv + dep > bound) return hv+dep;
    if (hv==0) {
               ans = true;
               final = a[7];
               return dep;
    }
    int next_bound = 10000;
    for (int i=1;i<=8;i++) {
        if (abs(c[i]-pre_move)==4) continue;   //与上一步相反的移动
        int tmp[25];
        for (int j=1;j<=24;j++) tmp[j]=a[j];
        trans(tmp,c[i]);
        stk[dep]=i;
        int new_bound = dfs(tmp,dep+1,c[i]);
        if (ans) return new_bound;
        next_bound = min(next_bound,new_bound);
    }
    return next_bound;
}
void ida_star() {
     memset(stk,0,sizeof(stk));
     bound = h(a);
     ans = false;
     while (!ans && bound<=100)
           bound = dfs(a,0,-100);
     for (int i=0;i<bound;i++) printf("%c",stk[i]+64);
     printf("\n%d\n",final);
}
int main() {
    while (~scanf("%d",&x)) {
          if (x==0) break;
          a[1]=x;
          for (int i=2;i<=24;i++)
              scanf("%d",&a[i]);
                  
          if (h(a)==0) {
                    printf("No moves needed\n");
                    printf("%d\n",a[7]);
                    continue;
          }
          ida_star();
    }
    return 0;
}