相当于模板题了，用trie来完成字符串到数字的映射比map<string, int>要快不少，令外可以考虑hash。
运行时间对比：
(1)(2)600ms左右 (3)3000ms左右(4)1500ms左右
（1）O(n^2)的dijkstra:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 | #include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <set>#include <map>#include <string>#include <math.h>#include <stdlib.h>#include <time.h>#include <map>using namespace std;#define umin(a, b) if ((a) > (b)) (a) = (b)const int maxn = 157;int n;struct Trie { int ch[maxn * 32][26]; int val[maxn * 32], sz; void init() { memset(val, 0, sizeof(val)); memset(ch[0], 0, sizeof(ch[0])); sz = 0; } int insert(char *s) { int i = 0, j = 0; for (; s[j]; i = ch[i][s[j]], j ++) { if (s[j] < ‘a‘) s[j] -= ‘A‘; else s[j] -= ‘a‘; if (!ch[i][s[j]]) { ch[i][s[j]] = ++ sz; memset(ch[sz], 0, sizeof(ch[sz])); } } if (!val[i]) val[i] = ++ n; return val[i]; }} trie;int dist[maxn][maxn], d[maxn];bool vis[maxn];int main(){#ifndef ONLINE_JUDGE freopen("in.txt", "r", stdin);#endif // ONLINE_JUDGE int m; char s1[40], s2[40]; int t; while (cin >> m, ~m) { n = 0; trie.init(); scanf("%s%s", s1, s2); trie.insert(s1); t = trie.insert(s2); memset(dist, 0x3f, sizeof(dist)); for (int i = 0; i < m; i ++) { int x; scanf("%s%s%d", s1, s2, &x); int u = trie.insert(s1), v = trie.insert(s2); umin(dist[u][v], x); umin(dist[v][u], x); } memset(vis, 0, sizeof(vis)); memset(d, 0x3f, sizeof(d)); d[1] = 0; for (int i = 1; i < n; i ++) { int pos = 0, mind = 0x3f3f3f3f; for (int j = 1; j <= n; j ++) { if (!vis[j] && d[j] < mind) { mind = d[j]; pos = j; } } if (!pos) break; vis[pos] = true; for (int j = 1; j <= n; j ++) { if (!vis[j]) umin(d[j], d[pos] + dist[pos][j]); } } printf("%d\n", d[t] == 0x3f3f3f3f? -1 : d[t]); } return 0;} |
（2）SPFA:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 | #include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <set>#include <map>#include <string>#include <math.h>#include <stdlib.h>#include <time.h>#include <map>using namespace std;#define umin(a, b) if ((a) > (b)) (a) = (b)const int maxn = 157;int n;struct Trie { int ch[maxn * 32][26]; int val[maxn * 32], sz; void init() { memset(val, 0, sizeof(val)); memset(ch[0], 0, sizeof(ch[0])); sz = 0; } int insert(char *s) { int i = 0, j = 0; for (; s[j]; i = ch[i][s[j]], j ++) { if (s[j] < ‘a‘) s[j] -= ‘A‘; else s[j] -= ‘a‘; if (!ch[i][s[j]]) { ch[i][s[j]] = ++ sz; memset(ch[sz], 0, sizeof(ch[sz])); } } if (!val[i]) val[i] = ++ n; return val[i]; }} trie;vector<vector<int> >G, W;queue<int> Q;int d[maxn];bool mark[maxn];bool relax(int u, int v, int w) { if (d[v] > d[u] + w) { d[v] = d[u] + w; return true; } return false;}int main(){#ifndef ONLINE_JUDGE freopen("in.txt", "r", stdin);#endif // ONLINE_JUDGE int m; char s1[40], s2[40]; int t; while (cin >> m, ~m) { n = 0; trie.init(); scanf("%s%s", s1, s2); trie.insert(s1); t = trie.insert(s2); G.clear(); W.clear(); G.resize(maxn + 2); W.resize(maxn + 2); for (int i = 0; i < m; i ++) { int x; scanf("%s%s%d", s1, s2, &x); int u = trie.insert(s1), v = trie.insert(s2); G[u].push_back(v); G[v].push_back(u); W[u].push_back(x); W[v].push_back(x); } while (!Q.empty()) Q.pop(); Q.push(1); memset(d, 0x3f, sizeof(d)); memset(mark, 0, sizeof(mark)); mark[1] = true; d[1] = 0; while (!Q.empty()) { int h = Q.front(); Q.pop(); for (int i = 0; i < G[h].size(); i ++) { int v = G[h][i], r = relax(h, v, W[h][i]); if (!mark[v] && r) { mark[v] = true; Q.push(v); } } mark[h] = false; } printf("%d\n", d[t] == 0x3f3f3f3f? -1 : d[t]); } return 0;} |
（3）map + cin :
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 | #include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <set>#include <map>#include <string>#include <math.h>#include <stdlib.h>#include <time.h>#include <map>using namespace std;const int maxn = 2e4 +7;map<string, int> mp;int n;vector<vector<int> >G, W;queue<int> Q;bool mark[maxn];int d[maxn];bool relax(int u, int v, int w) { if (d[v] > d[u] + w) { d[v] = d[u] + w; return true; } return false;}int main(){#ifndef ONLINE_JUDGE freopen("in.txt", "r", stdin);#endif // ONLINE_JUDGE string s1, s2, S; int x, m; while (cin >> m, ~m) { cin >> s1 >> s2; S = s2; n = 1; mp.clear(); G.clear(); W.clear(); G.resize(maxn + 2); W.resize(maxn + 2); if (!mp[s1]) mp[s1] = n ++; if (!mp[s2]) mp[s2] = n ++; for (int i = 0; i < m; i ++) { cin >> s1 >> s2 >> x; if (!mp[s1]) mp[s1] = n ++; if (!mp[s2]) mp[s2] = n ++; G[mp[s1]].push_back(mp[s2]); G[mp[s2]].push_back(mp[s1]); W[mp[s1]].push_back(x); W[mp[s2]].push_back(x); } while (!Q.empty()) Q.pop(); Q.push(1); memset(d, 0x3f, sizeof(d)); memset(mark, 0, sizeof(mark)); mark[1] = true; d[1] = 0; while (!Q.empty()) { int h = Q.front(); Q.pop(); for (int i = 0; i < G[h].size(); i ++) { int v = G[h][i], r = relax(h, v, W[h][i]); if (!mark[v] && r) { mark[v] = true; Q.push(v); } } mark[h] = false; } printf("%d\n", d[mp[S]] == 0x3f3f3f3f? -1 : d[mp[S]]); } return 0;} |
（4）map + scanf:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 | #include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <set>#include <map>#include <string>#include <math.h>#include <stdlib.h>#include <time.h>#include <map>using namespace std;const int maxn = 2e4 +7;map<string, int> mp;int n;vector<vector<int> >G, W;queue<int> Q;bool mark[maxn];int d[maxn];bool relax(int u, int v, int w) { if (d[v] > d[u] + w) { d[v] = d[u] + w; return true; } return false;}void read_string(string &s) { char s0[100]; scanf("%s", s0); s = string(s0);}int main(){#ifndef ONLINE_JUDGE freopen("in.txt", "r", stdin);#endif // ONLINE_JUDGE string s1, s2, S; int x, m; while (cin >> m, ~m) { read_string(s1); read_string(s2); S = s2; n = 1; mp.clear(); G.clear(); W.clear(); G.resize(maxn + 2); W.resize(maxn + 2); if (!mp[s1]) mp[s1] = n ++; if (!mp[s2]) mp[s2] = n ++; for (int i = 0; i < m; i ++) { read_string(s1); read_string(s2); scanf("%d", &x); if (!mp[s1]) mp[s1] = n ++; if (!mp[s2]) mp[s2] = n ++; G[mp[s1]].push_back(mp[s2]); G[mp[s2]].push_back(mp[s1]); W[mp[s1]].push_back(x); W[mp[s2]].push_back(x); } while (!Q.empty()) Q.pop(); Q.push(1); memset(d, 0x3f, sizeof(d)); memset(mark, 0, sizeof(mark)); mark[1] = true; d[1] = 0; while (!Q.empty()) { int h = Q.front(); Q.pop(); for (int i = 0; i < G[h].size(); i ++) { int v = G[h][i], r = relax(h, v, W[h][i]); if (!mark[v] && r) { mark[v] = true; Q.push(v); } } mark[h] = false; } printf("%d\n", d[mp[S]] == 0x3f3f3f3f? -1 : d[mp[S]]); } return 0;} |
原文：http://www.cnblogs.com/jklongint/p/4675180.html