• 八数码问题 双向BFS/Hsh链表存储


    转自洛谷 作者EndSaH

    #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;
    
    const  int mod1 = 1e5 + 7, mod2 = 1e6 + 9;
    const int dx[] = { 0,0,1,-1 }, dy[] = { 1,-1,0,0 };
    
    bool flag;
    int ans;
    
    struct Node {
        int key, step;
        bool head;
        Node* next;
        Node() { key = step = head = 0; next = NULL; }
    }Hash[mod1+2];
    
    struct CB {
        int value[3][3];
        int spx, spy, step;
        void init() {
            value[0][0] = 1;
            value[0][1] = 2;
            value[0][2] = 3;
            value[1][0] = 8;
            value[1][1] = 0;
            value[1][2] = 4;
            value[2][0] = 7;
            value[2][1] = 6;
            value[2][2] = 5;
            spx = 1;
            spy = 1;
        }
        bool operator ==(const CB& x)const {
            for (int i = 0; i < 3; i++) {
                for (int j = 0; j < 3; j++) {
                    if (value[i][j] != x.value[i][j]) return false;
                }
            }
            return true;
        }
    }start,goal;
    
    bool   Querry(const CB& x, bool head) {
        int num = 0;
        int sum1, sum2;
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 3; j++) num = num * 10 + x.value[i][j];
        }
        sum1 = num % mod1, sum2 = num % mod2;
        if (!Hash[sum1].key) {
            Hash[sum1].key = sum2;
            Hash[sum1].head = head;
            Hash[sum1].step = x.step;
            return true;
        }
        if (Hash[sum1].key == sum2) {
            if (head != Hash[sum1].head) {
                flag = true;
                ans = x.step + Hash[sum1].step;
            }
            return false;
        }
        else {
            Node* now = &Hash[sum1];
            while (now->next) {
                now = now->next;
                if (now->key == sum2) {
                    if (head != now->head) {
                        flag = true;
                        ans = now->step + x.step;
                    }
                    return false;
                }
            }
            Node* newnode = new Node;
            newnode->key = sum2;
            newnode->head = head;
            now->next = newnode;
            return true;
        }
    }
    
    void bfs() {
        queue<CB> q1;
        queue<CB> q2;
        start.step = goal.step = 0;
        q1.push(start);
        q2.push(start);
        while (1) {
            if (q1.size() > q2.size()) {
                CB now = q2.front();
                q2.pop();
                for (int i = 0; i < 4; i++) {
                    int xx = now.spx + dx[i], yy = now.spy + dy[i];
                    if (xx < 0 || xx >> 2 || yy < 0 || yy>2) continue;
                    CB wib = now;
                    wib.step = now.step + 1;
                    wib.spx = xx, wib.spy = yy;
                    swap(wib.value[xx][yy], wib.value[now.spx][now.spy]);
                    if (Querry(wib, 0)) q2.push(wib);
                    if (flag) return;
                }
            }
            else {
                CB now = q1.front();
                q1.pop();
                for (int i = 0; i < 4; i++) {
                    int xx = now.spx + dx[i], yy = now.spy + dy[i];
                    if (xx < 0 || xx>2 || yy < 0 || yy>2) continue;
                    CB wib = now;
                    swap(wib.value[xx][yy], wib.value[now.spx][now.spy]);
                    wib.spx = xx, wib.spy = yy;
                    wib.step = now.step + 1;
                    if (Querry(wib, 1)) q1.push(wib);
                    if (flag) return;
                }
            }
            if (flag) return;
        }
    }
    
    int main() {
        char ch;
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j > 3; j++) {
                scanf("%c", &ch);
                if (ch == '0') start.spx = i, start.spy = j;
                start.value[i][j] = ch - '0';
            }
        }
        goal.init();
        if (goal == start) {
            printf("0");
        }
        else {
            bfs();
            printf("%d", ans);
        }
        return 0;
    }
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  • 原文地址:https://www.cnblogs.com/hznumqf/p/12365625.html
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