Bellman-Ford（贝尔曼-福特）算法求单源最短路径

参考博客http://www.cnblogs.com/tanky_woo/archive/2011/01/17/1937728.html

/*
* About: Bellman-Ford算法
* Author: Tanky Woo
* Blog: www.WuTianqi.com
*/

#include <iostream>
using namespace std;
const int maxnum = 100;
const int maxint = 99999;

// 边，
typedef struct Edge{
int u, v; // 起点，重点
int weight; // 边的权值
}Edge;

Edge edge[maxnum]; // 保存边的值
int dist[maxnum]; // 结点到源点最小距离

int nodenum, edgenum, source; // 结点数，边数，源点

// 初始化图
void init()
{
// 输入结点数，边数，源点
cin >> nodenum >> edgenum >> source;
for(int i=1; i<=nodenum; ++i)
dist[i] = maxint;
dist[source] = 0;
for(int i=1; i<=edgenum; ++i)
{
cin >> edge[i].u >> edge[i].v >> edge[i].weight;
if(edge[i].u == source) //注意这里设置初始情况
dist[edge[i].v] = edge[i].weight;
}
}

// 松弛计算
void relax(int u, int v, int weight)
{
if(dist[v] > dist[u] + weight)
dist[v] = dist[u] + weight;
}

bool Bellman_Ford()
{
for(int i=1; i<=nodenum-1; ++i)
for(int j=1; j<=edgenum; ++j)
relax(edge[j].u, edge[j].v, edge[j].weight);
bool flag = 1;
// 判断是否有负环路
for(int i=1; i<=edgenum; ++i)
if(dist[edge[i].v] > dist[edge[i].u] + edge[i].weight)
{
flag = 0;
break;
}
return flag;
}
int main()
{
//freopen("input3.txt", "r", stdin);
init();
if(Bellman_Ford())
for(int i = 1 ;i <= nodenum; i++)
cout << dist[i] << endl;
return 0;
}