紫书p199 八数码(BFS,hash)

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八数码问题紫书上的简单搜索渣渣好久才弄懂
#include<cstdio>#include<cstring>using namespace std;const int M = 1000003;int x[4] = { -1, 1, 0, 0}, y[4] = {0, 0, -1, 1};int dis[M], h[M], s[M][9], e[9];int aton(int a[]){    int t = 0;    for(int i = 0; i < 9; ++i)        t = t * 10 + a[i];    return t;}int search_hash(int a[]){    int t = aton(a), p = t % M;    while(h[p])    {        if(h[p] == t) return p;        ++p;        if(p >= M) p = 0;    }    return p;}int bfs(){    memset(h, 0, sizeof(h));    int fro = 1, rear = 2, r, c, k = 0, p;    int t[9], tmp, cur, nr, nc, nk;    while(fro < rear)    {        memcpy(t, s[fro], sizeof(t));        cur = search_hash(t);        if(memcmp(t, e, sizeof(t)) == 0) return dis[cur];        for(k = 0; t[k];) ++k;        r = k / 3, c = k % 3;        for(int i = 0; i < 4; ++i)        {            memcpy(t, s[fro], sizeof(t));            nr = r + x[i], nc = c + y[i], nk = nr * 3 + nc;            if(nr < 0 || nr > 2 || nc < 0 || nc > 2) continue;            tmp = t[nk];            t[nk] = 0;            t[k] = tmp;            p = search_hash(t);            if(h[p] == 0)            {                h[p] = aton(t);                dis[p] = dis[cur] + 1;                memcpy(s[rear], t, sizeof(t));                ++rear;            }        }        ++fro;    }    return -1;}int main(){    while(~scanf("%d", &s[1][0]))    {        memset(dis, 0, sizeof(dis));        for(int i = 1; i < 9; ++i)            scanf("%d", &s[1][i]);        for(int i = 0; i < 9; ++i)            scanf("%d", &e[i]);        h[aton(s[1]) % M] = aton(s[1]);        int ans = bfs();        if(ans != -1)            printf("%d\n", ans);        else  printf("No solution\n");    }    return 0;}/*2 6 4 1 3 7 0 5 88 1 5 7 3 6 4 0 22 3 4 1 5 0 7 6 81 2 3 4 5 6 7 8 0*/
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