[英]Dijkstra's Algorithm using Adjacency Matrix not finding correct distance/path from each node to every other node
[英]Dijksta's Algorithm not finding path in Adjacency Matrix
由於某種原因,當我在隨機生成的矩陣上運行dijkstra的算法時,即使很明顯它是一個連通圖,它也找不到所有節點之間的路徑。 我已經打印出圖表,並且它們始終遵循此表格
0--2--3
| | |
4--5--6
| | |
7--8--9
現在,我僅使用3 * 3矩陣,並試圖使其正常工作。 下面的代碼創建一個具有9個節點的鄰接矩陣,並隨機生成一個介於1和3之間的數字以表示邊緣的權重。 我用4表示無窮大。 源被硬編碼為0和numOfVertices 9
#include<iostream>
#include <time.h>
#include <math.h>
#define INFINITY 4
#define V 9
using namespace std;
class Dijkstra{
private:
int predecessor[20],distance[20];
bool mark[20];
int source;
int destination;
int numOfVertices;
char gameMode;
public:
int adjMatrix[9][9];
void read();
void initialize();
void setSource(int k);
int getClosestUnmarkedNode();
void calculateDistance();
void output();
int randomEdge();
int randomNode();
void printPath(int);
};
void Dijkstra::read(){
numOfVertices = 4;
for(int i = 0; i < numOfVertices;i++){
for(int j = 0; j < numOfVertices;j++){
if(i == j)
adjMatrix[i][j] = 0;
else if(j >= i){
if(j == i + 1 || j == i - 1 || j == i + sqrt((double)numOfVertices)|| j == i - sqrt((double)numOfVertices))
adjMatrix[i][j] = randomEdge();
else
adjMatrix[i][j] = 4;
if((i % ((int)sqrt((double)numOfVertices)) == ((int)sqrt((double)numOfVertices)) - 1) && j == i + 1)
adjMatrix[i][j] = 4;
}
else
adjMatrix[i][j] = adjMatrix[j][i];
cout<<adjMatrix[i][j]<< " ";
}
cout<< "\n";
}
source = 0;
}
void Dijkstra::initialize(){
for(int i=0;i<numOfVertices;i++) {
mark[i] = false;
predecessor[i] = -1;
distance[i] = INFINITY;
}
distance[source]= 0;
}
int Dijkstra::getClosestUnmarkedNode(){
int minDistance = INFINITY;
int closestUnmarkedNode = 0;
for(int i=0;i<numOfVertices;i++) {
if((!mark[i]) && ( minDistance >= distance[i])) {
minDistance = distance[i];
closestUnmarkedNode = i;
}
}
return closestUnmarkedNode;
}
void Dijkstra::calculateDistance(){
initialize();
int minDistance = INFINITY;
int closestUnmarkedNode;
int count = 0;
while(count < numOfVertices) {
closestUnmarkedNode = getClosestUnmarkedNode();
mark[closestUnmarkedNode] = true;
for(int i=0;i<numOfVertices;i++) {
if((!mark[i]) && (adjMatrix[closestUnmarkedNode][i]>0) ) {
if(distance[i] > distance[closestUnmarkedNode]+adjMatrix[closestUnmarkedNode][i]) {
distance[i] = distance[closestUnmarkedNode]+adjMatrix[closestUnmarkedNode][i];
predecessor[i] = closestUnmarkedNode;
}
}
}
count++;
}
}
void Dijkstra::printPath(int node){
if(node == source)
cout<<node<<"..";
else if(predecessor[node] == -1)
cout<<"No path from "<<source<<"to "<<node<<endl;
else {
printPath(predecessor[node]);
cout<<node<<"..";
}
}
void Dijkstra::output(){
for(int i=0;i<numOfVertices;i++) {
if(i == source)
cout<<source<<".."<<source;
else
printPath(i);
cout<<"->"<<distance[i]<<endl;
}
}
int Dijkstra::randomEdge(){
return rand() % 3 + 1;
}
void Dijkstra::setSource(int k){
source = k;
}
int main(int argc, char** argv){
Dijkstra G;
G.read();
G.calculateDistance();
G.output();
int k;
cin>> k;
exit(0);
}
您使用4表示無限距離...但是4是沿有效路徑容易達到的距離。 該代碼拒絕總距離> = 4的任何路徑,因為每個節點的起點與源的距離最大為4(即不可達)。
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