虽然我想说，这貌似是。。。可以直接dfs做的。。。
但是还是Dinic最大流保险一点。。。
板子补完中→_→
1 /************************************************************** 2 Problem: 3396 3 User: rausen 4 Language: C++ 5 Result: Accepted 6 Time:0 ms 7 Memory:824 kb 8 ****************************************************************/ 9 10 #include <cstdio> 11 #include <cctype> 12 #include <cstring> 13 #include <algorithm> 14 15 using namespace std; 16 const int inf = (int) 1e9; 17 const int N = 65; 18 const int M = 1505; 19 20 struct edges{ 21 int next, to, f; 22 edges() {} 23 edges(int _next, int _to, int _f) : next(_next), to(_to), f(_f) {} 24 } e[M]; 25 26 int n; 27 int first[N], tot = 1, d[N], q[N]; 28 int S, T; 29 30 inline int read() { 31 int x = 0; 32 char ch = getchar(); 33 while (ch < '0' || '9' < ch) 34 ch = getchar(); 35 while ('0' <= ch && ch <= '9') { 36 x = x * 10 + ch - '0'; 37 ch = getchar(); 38 } 39 return x; 40 } 41 42 inline char getc() { 43 char ch = getchar(); 44 while (!isalpha(ch)) 45 ch = getchar(); 46 return ch; 47 } 48 49 inline void add_edge(int x, int y, int z){ 50 e[++tot] = edges(first[x], y, z); 51 first[x] = tot; 52 } 53 54 inline void Add_Edges(int x, int y, int z){ 55 add_edge(x, y, z); 56 add_edge(y, x, 0); 57 } 58 59 bool bfs(){ 60 memset(d, 0, sizeof(d)); 61 q[1] = S, d[S] = 1; 62 int l = 0, r = 1, x, y; 63 while (l < r){ 64 ++l; 65 for (x = first[q[l]]; x; x = e[x].next){ 66 y = e[x].to; 67 if (!d[y] && e[x].f) 68 q[++r] = y, d[y] = d[q[l]] + 1; 69 } 70 } 71 return d[T]; 72 } 73 74 int dinic(int p, int limit){ 75 if (p == T || !limit) return limit; 76 int x, y, tmp, rest = limit; 77 for (x = first[p]; x; x = e[x].next){ 78 y = e[x].to; 79 if (d[y] == d[p] + 1 && e[x].f && rest){ 80 tmp = dinic(y, min(rest, e[x].f)); 81 rest -= tmp; 82 e[x].f -= tmp, e[x ^ 1].f += tmp; 83 if (!rest) return limit; 84 } 85 } 86 if (limit == rest) d[p] = 0; 87 return limit - rest; 88 } 89 90 int Dinic(){ 91 int res = 0, x; 92 while (bfs()) 93 res += dinic(S, inf); 94 return res; 95 } 96 97 int main() { 98 char ch; 99 int i, x, y, z; 100 n = read(); 101 for (i = 1; i <= n; ++i) { 102 ch = getc(); 103 if ('A' <= ch && ch <= 'Z') 104 x = ch - 'A' + 1; 105 else x = ch - 'a' + 27; 106 ch = getc(); 107 if ('A' <= ch && ch <= 'Z') 108 y = ch - 'A' + 1; 109 else y = ch - 'a' + 27; 110 z = read(); 111 Add_Edges(x, y, z); 112 } 113 S = 1, T = 26; 114 printf("%d ", Dinic()); 115 return 0; 116 }
（p.s. 为毛线。。。之前的Dinic写错了还过了？233）