八数码问题 IDA*搜索

#include<iostream>
#include<string>
#include<cmath>
#include<cstring>
#include<vector>
#include<map>
#include<set>
#include<algorithm>
#include<queue>
#include<stack>
#include<sstream>
#include<cstdio>
#define INF 0x3f3f3f3f
//const int maxn = 1e6 + 5;
const double PI = acos(-1.0);
typedef long long ll;
using namespace std;

char ss[];
int ans[][] = {
    {,,,},
    {,,,},
    {,,,},
    {,,,}
};
int a[][];
int k, judge;
int dx[] = { ,,-, };
int dy[] = { ,,,- };

int check() {
    for (int i = ; i <= ; i++) {
        for (int j = ; j <= ; j++) {
            if (ans[i][j] != a[i][j]) return ;
        }
    }
    return ;
}

int test(int step) {
    int cnt = ;
    for (int i = ; i <= ; i++) {
        for (int j = ; j <= ; j++) {
            if (ans[i][j] != a[i][j]) {
                if (++cnt + step > k) return ;
            }
        }
    }
    return ;
}

void A_star(int step, int x, int y, int pre) {
    if (step == k) {
        if (check()) judge = ; return;
    }
    if (judge) return;
    for (int i = ; i < ; i++) {
        int xx = x + dx[i], yy = y + dy[i];
        if (xx <  || xx> || yy <  || yy> || pre + i == ) continue;
        swap(a[x][y], a[xx][yy]);
        if (test(step) && !judge) A_star(step + , xx, yy, i);
        swap(a[x][y], a[xx][yy]);
    }
}

int main() {
    int x, y;
    scanf("%s",ss);
    for (int i = ; i < ; i++) {
        a[i /  + ][i %  + ] = ss[i] - '';
        if (ss[i] - '' == ) x = i /  + , y = i %  + ;
    }
    if (check()) {
        printf("0\n");
    }
    else {
        while (++k) {
            A_star(, x, y, -);
            if (judge) {
                printf("%d", k);
                break;
            }
        }
    }
    return ;
}