HDU-3567 Eight II (DBFS+康托展开）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=3567
参考代码：https://www.xuebuyuan.com/3266380.html

学习双向广搜好难啊~~时间似乎也不够快
本题最难的点在于如何按字典序来输出
根据上面参考的博客发现最重要的点有：
1.当反向bfs找到时直接跳过这一步，因为不能把正向bfs的结果覆盖掉；
2.反向找的时候出现了重复要判断该次重复是否能构成更小的字典序；
3.要设置层数L，必须是两个都得一层一层来，不然会WA。

字典序之外还有：当输入的数据两行相同时，要输出走了0步，并且输出一行空行。
此外我还犯了个小错误把factory数组中的40320打成了40230导致有少部分数据的输出结果错误。

代码如下：

#include<cstdio>
#include<cstring>
#include<string>
#include<queue>
#include<vector>
using namespace std;
const int factory[] = { 1,1,2,6,24,120,720,5040,40320,362880 };
const int dr[] = { 1,0, 0, -1 };//dlru
const int dc[] = { 0 ,-1 ,1,0 };
const char* str = "dlru";
const int maxn = 362880 + 5;
int s[9], e[9];
char tag[maxn];
string lu[maxn];
int cantor(const int(&a)[9]) {
    int ret = 0;
    for (int i = 0; i < 9; i++) {
        int rank = 0;
        for (int j = i + 1; j < 9; j++)
            if (a[i] > a[j])rank++;
        ret += rank * factory[8 - i];
    }
    return ret + 1;
}
inline void read(int& x) {
    char ch = getchar();
    while (ch == ' ' || ch == '\n')ch = getchar();
    if (ch == 'X')ch = '0';
    x = ch - '0';
}
bool check(int x, int y) {
    if (x < 0 || x >= 3 || y < 0 || y >= 3)return false;
    return true;
}
void make_tag(int kt, char tip) {
    tag[kt] = tip;
}
char get_tag(int kt) {
    return tag[kt];
}
struct node {
    int state[9], kt, deep;
};
void DBFS() {
    memset(tag, 0, sizeof(tag));
    node u, v;
    memcpy(u.state, s, sizeof(s));
    memcpy(v.state, e, sizeof(e));
    u.kt = cantor(u.state);
    v.kt = cantor(v.state);
    u.deep = v.deep = 0;
    if (u.kt == v.kt) {
        printf("0\n\n");
        return;
    }
    lu[u.kt] = "";
    lu[v.kt] = "";
    make_tag(u.kt, '1');
    make_tag(v.kt, '2');
    queue<node>q, t;
    q.push(u);
    t.push(v);
    int L = 0;
    while (!q.empty() || !t.empty()) {
        int pos, pos2, px, py;
        while (q.front().deep == L) {
            u = q.front(); q.pop();
            for (pos = 0; u.state[pos]; pos++);
            px = pos / 3; py = pos % 3;
            for (int i = 0; i < 4; i++) {
                int row = px + dr[i];
                int col = py + dc[i];
                if (!check(row, col))continue;
                pos2 = row * 3 + col;
                v = u;
                swap(v.state[pos], v.state[pos2]);
                v.kt = cantor(v.state);
                v.deep = u.deep + 1;
                if (get_tag(v.kt) == '2') {
                    printf("%d\n%s\n", lu[u.kt].size() + lu[v.kt].size() + 1, (lu[u.kt] + str[i] + lu[v.kt]).c_str());
                    return;
                }
                else if (get_tag(v.kt) == '1')continue;
                lu[v.kt] = lu[u.kt] + str[i];//父节点
                make_tag(v.kt, '1');
                q.push(v);
            }
        }
        while (t.front().deep == L) {
            u = t.front(); t.pop();
            for (pos = 0; u.state[pos]; pos++);
            px = pos / 3; py = pos % 3;
            for (int i = 0; i < 4; i++) {
                int row = px + dr[i];
                int col = py + dc[i];
                if (!check(row, col))continue;
                pos2 = row * 3 + col;
                v = u;
                swap(v.state[pos], v.state[pos2]);
                v.deep = u.deep + 1;
                v.kt = cantor(v.state);
                if (get_tag(v.kt) == '1')continue;
                if (get_tag(v.kt) == '2' && lu[v.kt][0] < str[3 - i]) continue;
                lu[v.kt] = str[3 - i] + lu[u.kt];//父节点
                make_tag(v.kt, '2');
                t.push(v);
            }
        }
        L++;
    }
}
int main(void) {
    int T; scanf("%d", &T);
    for (int kase = 1; kase <= T; kase++) {
        for (int i = 0; i < 9; i++)read(s[i]);
        for (int i = 0; i < 9; i++)read(e[i]);
        printf("Case %d: ", kase);
        DBFS();
    }
    return 0;
}

需要更多的数据可以去hdu的discuss里或者点击上述博客网址找数据生成器😜

给出一组测试数据：

203
12X453786
12345678X
564178X23
7568X4123
12345678X
12345678X
783X64215
73862X541
7546318X2
X61357842
3465827X1
5316428X7
5724368X1
37X645281
63X574281
78345X621
362X84175
285X74316
7234586X1
2138X7654
635X24178
751X38462
327X86145
X21653478
7X8132456
632X74185
X65721843
834765X21
X38716254
1X5782463
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5236X8174
8625X7431
785X13642
741X53682
65412X378
2746183X5
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43X516278
27685143X
146832X57
254687X31
513674X28
231486X57
87156423X
6134X5728
8132456X7
35482167X
637X84251
8716X2453
5X3728461
57X681432
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85X327146
2435618X7
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48573126X
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487X25613
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4132X8675
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58X126473
241567X38
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314786X25
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1358426X7
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1857X3246
1523X8746
5318427X6
1256347X8
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46375218X
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8543172X6
83512674X
8X7513624
6X4123785
871X65324
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468X21357
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237X58641
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1452376X8
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528614X37
8164X2735
42X357186

数据答案：

Case 1: 2
dd
Case 2: 8
urrulldr
Case 3: 0
 
Case 4: 18
rdrululddrrullurrd
Case 5: 17
ruulldrrdluurdlul
Case 6: 22
ruulldrdluurdrulldrrdl
Case 7: 23
uurdluldrdlururdluldrur
Case 8: 17
lddluurdrdllurdru
Case 9: 20
rrdluurddlulurdrdllu
Case 10: 23
rulldrrulldrulurdldrrul
Case 11: 24
drurdluldrrululdrurddlul
Case 12: 21
druuldrrulldrrdlurull
Case 13: 24
ddluurrddlurdllurulddrul
Case 14: 22
drdluurddruulddluurdld
Case 15: 25
ddrruuldldrulurdrulddrulu
Case 16: 18
ddrulurddluurdrdlu
Case 17: 19
lurdrulddrullurddlu
Case 18: 22
rruldrdluulddruulddrur
Case 19: 21
uuldrrdlluurdrulddluu
Case 20: 26
dldlururdldruuldlurddlurdr
Case 21: 24
ruurdllurrdlldrulurdrdll
Case 22: 24
rrululddrrululddruurdlld
Case 23: 22
lluruldrrdllururdldrul
Case 24: 15
uurdldrullurrdd
Case 25: 23
rrdluurdlldrruuldlurrdl
Case 26: 23
druldlurddruulldrdrulur
Case 27: 20
rdruldrdluruldrdlulu
Case 28: 21
dllurdrulddluurddruld
Case 29: 26
ldrurdluurddluulddruuldrrd
Case 30: 21
lurrdlldrulurdrdlluur
Case 31: 23
urrddllurdluurdrdllurul
Case 32: 18
ddlurulddruuldrrul
Case 33: 25
drurullddrruulldrdruulldr
Case 34: 17
urdluurrdluldrurd
Case 35: 19
rrddluurddlluruldrd
Case 36: 23
rddluurddruldluurdruldd
Case 37: 24
lurrdlluurdrulddluurdrul
Case 38: 24
lddruuldldrrulurdllurddl
Case 39: 18
rululddrrululddrur
Case 40: 20
druulddluurddruuldld
Case 41: 20
ddlurdrulurdlulddrru
Case 42: 23
drulurdruldlurrdldlurdr
Case 43: 21
uurdrulddluurddruuldd
Case 44: 26
druurddllurrulddluurdruldd
Case 45: 21
lurdlulddrurdluldruul
Case 46: 14
rdllurdrulurdl
Case 47: 26
rulldrulurrddlulurdruldldr
Case 48: 24
rdrdluurddluldrrullurddr
Case 49: 17
ldluurrdllurdldru
Case 50: 17
uldrruulddrulldrr
Case 51: 26
rddlluurddluurdrdlluurdrul
Case 52: 15
rurdllurrdldluu
Case 53: 27
rdrdlluurdrulddluurddruldlu
Case 54: 19
ldluurdrdlluurdrdll
Case 55: 22
uurdluldrdruulldrdluru
Case 56: 24
drullurdldrruuldlurddruu
Case 57: 26
rurdlluurddlurrdluuldrurdd
Case 58: 17
uurdllurrddluruld
Case 59: 25
dluldrurdldrullurdldruuld
Case 60: 27
ddlluurrdldrullurrddlulurdl
Case 61: 24
dluurrddlluurdrdlluurddl
Case 62: 18
lurrdlluruldrurdll
Case 63: 26
ddruldlurdruulldrrulldrrdl
Case 64: 19
ulurdruldlurdruldld
Case 65: 21
drulurdrdlluurdldruru
Case 66: 25
lurrdluulddruurddluurdldl
Case 67: 21
drruuldlurrdldlurdruu
Case 68: 20
ddruuldldrulurrdldru
Case 69: 16
llururddllurrdlu
Case 70: 24
dlluurddruulddruldluurdl
Case 71: 25
lddrullurrdluldrdluruldru
Case 72: 23
rdlurrdlurullddruruldlu
Case 73: 23
rdluurdldrurullddrruldl
Case 74: 24
dlurdlldrruldlururdluldd
Case 75: 22
dllurrdlurullddruurdld
Case 76: 15
dllurrullddruld
Case 77: 16
dluurdrulddruull
Case 78: 22
ddrurulddruuldlurddruu
Case 79: 25
dllurdluurrdluldrurddluur
Case 80: 23
luurdlldrrullurrdldluru
Case 81: 25
drdruldlurdrululddrruuldl
Case 82: 27
drruldruulldrrulldrdruuldld
Case 83: 21
uurrddluulddrulurdrul
Case 84: 22
lurrdllurrddlurdllurdr
Case 85: 25
llurrdlluurdruldrdluldrur
Case 86: 23
rdldrulurrddluurddluurd
Case 87: 19
uldldrurdllurdruull
Case 88: 22
dllurddlurdruulldrdrul
Case 89: 23
rululddruurdlulddruurdd
Case 90: 23
lururdluldrdluurdrulddr
Case 91: 26
uurrddlurdlluruldrurddluld
Case 92: 19
druulldrurdldruuldl
Case 93: 23
uldldrrulldruurdllurrdl
Case 94: 15
lurddluldrurull
Case 95: 22
ldluruldrruldrdluruldr
Case 96: 26
lurrdllurrulldrrulddruldlu
Case 97: 23
lururddlluurdrdluldruul
Case 98: 22
drrullurddlurdruulldrr
Case 99: 21
ruldluurdldrruullddru
Case 100: 25
urulddrullurdldruurddluul
Case 101: 22
drrulldruurddllurdluur
Case 102: 19
urdrulldrdruulddruu
Case 103: 23
ddllurdruldluruldrdluur
Case 104: 19
uldrdlurrulldrruldr
Case 105: 20
ldrdluurdluldrurddll
Case 106: 20
ullddruuldrurddlluru
Case 107: 20
ldrurdluldruurddlulu
Case 108: 21
rrululddruurdllurdrul
Case 109: 24
rdlurrddllurulddrurdllur
Case 110: 24
lurdlulurrddluldruulddru
Case 111: 17
uulddrulurdllurdl
Case 112: 20
druldrdruulldrdruuld
Case 113: 24
rullddrurdlulurrdlulddrr
Case 114: 23
dldlurrdluulddruurddluu
Case 115: 25
dlldrulurdldrruulddlurrdl
Case 116: 20
druldrdllurdruulddru
Case 117: 23
rrulldrrulldruurddluuld
Case 118: 8
dllurdld
Case 119: 26
rulldrurddlurdllurulddruur
Case 120: 24
llurdruuldrdllurrdllurrd
Case 121: 26
ruldrrullurrdllurddluurddr
Case 122: 25
dldlurrdluurddluurdllurdl
Case 123: 23
lddrullurdldruulddrruul
Case 124: 20
uulddlurdruullddrurd
Case 125: 23
rruullddrrulldrruuldlur
Case 126: 24
ddlluurdrdllurrdlluurdld
Case 127: 21
ulldruurdluldrdruulld
Case 128: 23
ruurdlldrruldluruldrdlu
Case 129: 13
llurddruulddl
Case 130: 24
ruulddruruldldrruulddlur
Case 131: 22
ruulldrdlururdluldrurd
Case 132: 18
uruldrrulddluurdrd
Case 133: 23
ddrrululddrrululddrruld
Case 134: 23
drdlluruldrruldrdlluurr
Case 135: 23
rullddruulddrurdluldruu
Case 136: 23
ddlluruldrdlururddlurul
Case 137: 18
rrdllurrddluurddlu
Case 138: 24
ulldrrululddruuldrrdllur
Case 139: 21
ruulddlurdrulldrulurr
Case 140: 19
ulldrulurrdldrulurd
Case 141: 25
rdrulldruuldrurdlulddruru
Case 142: 21
rdlurrdldrulldrrulurd
Case 143: 24
rdluurddlulurrddlluurdrd
Case 144: 22
uurrddllurdluurdrdlulu
Case 145: 24
rurddluldruulddrurdlluru
Case 146: 23
druurddluuldrrullddrrul
Case 147: 20
lddruulldrrulldrurdd
Case 148: 22
ldrulurdrdllurrulldrru
Case 149: 24
urdrulddluurdrdllurdluur
Case 150: 25
rruullddrrululddruldrruul
Case 151: 17
dllurulddrrululdr
Case 152: 25
ruldluruldrurddluurddluld
Case 153: 13
lulurrdluldrr
Case 154: 24
luurdllurdldrulurrddlurd
Case 155: 15
ldrululddrulurr
Case 156: 26
lluurrdllurddluurrddlurdll
Case 157: 19
luurdldrruldruulddl
Case 158: 16
rurullddrruuldru
Case 159: 23
llurddlurruldrdluulddrr
Case 160: 26
drdlurrdluurddluuldrdlurul
Case 161: 21
dluurdrulddruuldldrru
Case 162: 18
ldldrruullddrrulur
Case 163: 21
dluurdlldrruulldrurdl
Case 164: 26
dlurrdllururddluldruurddll
Case 165: 26
llurrdluruldrdlurulldrrull
Case 166: 24
ddlulurrddluurddlulurrdd
Case 167: 23
ruurdllurrddluruldlurrd
Case 168: 18
uuldlurrdllurddruu
Case 169: 21
drulddruurddlurulldru
Case 170: 19
lldrrdlluurdrulddru
Case 171: 20
ddluurddllurdrululdr
Case 172: 22
urdldluurddruulddlurru
Case 173: 25
rurdlulddrrulldruulddruul
Case 174: 16
rrdldluurddruldr
Case 175: 21
ululddruldrruuldldrur
Case 176: 22
ddluurdrdluruldlurddru
Case 177: 23
dldrulurrdlulddruulddru
Case 178: 11
drdluurdldr
Case 179: 22
dluldrurdllurdldrrulld
Case 180: 24
dlluruldrrdllururddluurd
Case 181: 22
urrdlluurdrulldrdrulur
Case 182: 24
rrdldluurddlurrdlluurrdl
Case 183: 28
rrddllurrdllurrdluuldrurdldr
Case 184: 17
drullddrurdllurdl
Case 185: 24
druuldrrdlluurrdldluruld
Case 186: 22
rdruldrdllurdruulddruu
Case 187: 24
dllurrdluulddrulurrdluld
Case 188: 24
ddlurruldrdllurrulddruul
Case 189: 24
uldrruldrdllurdrululdrur
Case 190: 24
rdrullddrurdluldrrullurr
Case 191: 23
ddrruuldlurddlurrdluuld
Case 192: 25
urrdllurdluurrdllurrdldlu
Case 193: 16
luruldldrruldlur
Case 194: 21
uurddlurruldrdlulurrd
Case 195: 18
dlluruldrrullddrur
Case 196: 20
rurddluulddruulddrur
Case 197: 19
lluurddlurrullddrur
Case 198: 27
lurddluulddruuldrrdllurrull
Case 199: 19
drrdluurddluurdluld
Case 200: 20
drurddllururdldrulur
Case 201: 17
ruldruulldrrulldd
Case 202: 22
rrululdrrulddruuldrdll
Case 203: 24
ulddruurdlldrrulurdldruu