标签：const ted ice std lin find contain define elf
题目链接：http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=GRL_1_C
An edge-weighted graph G (V, E).
|V| |E| s0 t0 d0 s1 t1 d1 : s|E|?1 t|E|?1 d|E|?1
|V| is the number of vertices and |E| is the number of edges in G. The graph vertices are named with the numbers 0, 1,..., |V|?1 respectively.
si and ti represent source and target vertices of i-th edge (directed) and di represents the cost of the i-th edge.
If the graph contains a negative cycle (a cycle whose sum of edge costs is a negative value), print
NEGATIVE CYCLE
in a line.
Otherwise, print
D0,0 D0,1 ... D0,|V|?1 D1,0 D1,1 ... D1,|V|?1 : D|V|?1,0 D1,1 ... D|V|?1,|V|?1
The output consists of |V| lines. For each ith line, print the cost of the shortest path from vertex i to each vertex j (j=0,1,…|V|?1) respectively. If there is no path from vertex i to vertex j, print "INF". Print a space between the costs.
4 6 0 1 1 0 2 5 1 2 2 1 3 4 2 3 1 3 2 7
0 1 3 4 INF 0 2 3 INF INF 0 1 INF INF 7 0
4 6 0 1 1 0 2 -5 1 2 2 1 3 4 2 3 1 3 2 7
0 1 -5 -4 INF 0 2 3 INF INF 0 1 INF INF 7 0
4 6 0 1 1 0 2 5 1 2 2 1 3 4 2 3 1 3 2 -7
NEGATIVE CYCLE
这题先用Bellman-Ford算法判断负圈，再用Floyd-Warshall算法求任意两点间的最短路即可。
代码：
#include <iostream> #include <algorithm> #include <map> #include <vector> using namespace std; typedef long long ll; #define INF 2147483647 struct edge{ int from,to,cost; }; edge es[10000]; int d[110][110]; // d[i][j]表示点i到点j的最短路径 int V,E; //点和边的数量 //判断负圈 bool find_negative_loop(){ int s[110]; fill(s,s+V,0); for(int i = 0;i < V; i++){ for(int j = 0;j < E; j++){ edge e = es[j]; if(s[e.to] > s[e.from] + e.cost){ s[e.to] = s[e.from] + e.cost; if(i == V-1) return false; } } } return true; } //任意两点间最短路径 void warshall_floyd(){ for(int k = 0;k < V; k++){ for(int i = 0;i < V; i++){ for(int j = 0;j < V; j++){ if(d[i][k] != INF && d[k][j] != INF) d[i][j] = min(d[i][j], d[i][k] + d[k][j]); } } } } int main(){ cin >> V >> E; for(int i = 0;i < V; i++){ for(int j = 0;j < V; j++){ d[i][j] = INF; } d[i][i] = 0; } for(int i = 0;i < E; i++) cin >> es[i].from >> es[i].to >> es[i].cost,d[es[i].from][es[i].to] = es[i].cost; if(find_negative_loop()){ warshall_floyd(); for(int i = 0;i < V; i++){ for(int j = 0;j < V; j++){ if(j != 0) cout << " "; if(d[i][j] == INF) cout << "INF"; else cout << d[i][j]; } cout << endl; } }else{ cout <<"NEGATIVE CYCLE" <<endl; } return 0; }
AOJ GRL_1_C: All Pairs Shortest Path (Floyd-Warshall算法求任意两点间的最短路径)（Bellman-Ford算法判断负圈）
标签：const ted ice std lin find contain define elf
原文地址：http://www.cnblogs.com/zhangjiuding/p/7726315.html
