CODEVS-1018单词接龙

 1 /*
 2     string类稍微方便一些，记得最后比较长度
 3 */
 4 #include<iostream>
 5 #include<algorithm>
 6 #include<string>
 7 using namespace std;
 8 
 9 string str[44];
10 int mark[44], label[44], len[44], sum, n, ans;
11 char c;
12 
13 //mark标记是否用过该字母，label记住该字母在str数组中下标，len记住该字母长度
14 void dfs(int k)
15 {
16     if (k == 1){//确定首位
17         for (int i = 1; i <= 2 * n; i += 2){
18             if (mark[i] == 0 && str[i][0] == c){
19                 sum += str[i].length(); mark[i] = 1; label[k] = i; len[k] = str[i].length();
20                 dfs(k + 1);
21                 sum -= len[k]; mark[i] = 0;//回到上一步，清除标志
22             }
23         }
24     }
25     else{
26         for (int i = 1; i <= 2 * n; i++){//这里是i++表示每个字母都会遍历两遍
27             if (mark[i] == 0){
28                 bool judge = false;
29                 int pre = label[k - 1], j;
30                 int len1 = str[pre].length(), len2 = str[i].length();
31                 int Len = min(len1, len2);//字符串不能包含，题意
32                 for (j = 1; j < Len; j++)
33                 {   //substr函数返回子字符串，（开始位置，长度）
34                     if (str[pre].substr(len1 - j, j) == str[i].substr(0, j))
35                     {
36                         judge = true;
37                         break;
38                     }
39                 }
40                 if (judge)
41                 {
42                     mark[i] = 1; label[k] = i; len[k] = len2 - j; sum += len[k];
43                     dfs(k + 1);
44                     mark[i] = 0; sum -= len[k];//回到上一步，清除标记
45                 }
46             }
47         }
48     }
49     ans = max(ans, sum);//最后比较最长是多少
50 }
51 int main()
52 {
53     cin >> n;
54     for (int i = 1; i <= 2 * n; i += 2){
55         cin >> str[i];
56         str[i + 1] = str[i];//每个字母最多使用两次
57     }
58     cin >> c;
59     dfs(1);
60     cout << ans << endl;
61     return 0;
62 }