Re-discussion on Bellman-ford algorithm

Prerequisites: Understanding the Bellman-ford algorithm

Basic model:

#include <iostream>using namespace std; #define INF 0x7fffffff#define Maxx 100int G[maxx][maxx],dis[maxx];int n,m; int min (int a,int b) {return (A&GT;B?B:A);}        void init (int n) {for (int i=1;i<=n;i++) {dis[i]=0;    for (int j=1;j<=n;j++) g[i][j]= (I==j?0:inf);    }}void Bellman_fory () {for (int i=1;i<=n;i++) dis[i]=g[1][i];    dis[1]=0;        for (int k=2;k<=n;k++)//From Dist (1) [i] Hand eject dist (2) [I],..., Dist (n-1) [i] {for (int i=1;i<=n;i++)//modify Dist[i per vertex] {if (i!=1) for (int j=1;j<=n;j++) {//Vertex J to I have a direct path and pass vertices J can make Dist[i] shorten if (G[j][i]<inf&&dis[i]>dis[j]+g[j][i]) dis[i]=dis[j                ]+g[j][i]; }}}/* To determine if there is a negative weight loop for (int i=1;i<=n;i++) {for (int j=1;j<=n;j++) {if (G I        [J]<inf&&dis[j]>dis[i]+g[i][j]) return false; } RETurn true;    } */}int Main () {cin>>n>>m;    int a,b,c;    Init (n);        for (int i=1;i<=m;i++) {cin>>a>>b>>c;    G[a][b]=c;    } bellman_fory ();    for (int i=1;i<=n;i++) cout<<dis[i]<< ""; Cout<<endl;}

Further discussion:

Implemented with Adjacency table (complexity is O (n^2))

#include <iostream>using namespace std; #define INF 0x7fffffff#define maxx 1010typedef struct edge{int u,v; int weight;} Edge;    Edge Edge[maxx];int dist[maxx];int n,e,s;//node, edge number, source point void init () {cin>>n>>e>>s;    for (int i=1;i<n;i++) Dist[i]=inf;    dist[s]=0;        for (int i=1;i<=e;i++) {cin>>edge[i].u>>edge[i].v>>edge[i].weight;    if (edge[i].u==s) dist[edge[i].v]=edge[i].weight; }}bool Bellman_ford () {for (Int. i=1;i<=n-1;i++) for (int j=1;j<=n;j++) if (EDGE[J].WEIGHT&LT;INF&A    Mp;&dist[edge[j].v]>dist[edge[j].u]+edge[j].weight) Dist[edge[j].v]=dist[edge[j].u]+edge[j].weight;    BOOL flag = 1; for (int i=1;i<e;i++) if (Edge[j].weight<inf&&&&dist[edge[i].v]>dist[edge[i].u]+edge[i].            Weight) {flag = 0;        Break } return flag;    int main () {init (); if (Bellman_ford ()) for (int i=1;i<=n;i++) cout<<dist[i]<<endl;    else cout<< "No" <<endl; return 0;}

Test examples:

7 10
1 2 6
1 3 5
1 4 5
2 5-1
3 2-2
3 5 1
4 3-2
4 6-1
5 7 3
6 7 3

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Re-discussion on Bellman-ford algorithm