Dijkstra算法无法正确输出

Question

I am having trouble with implementing Dijkstra algorithm.

I have the following variables initialized :

enum GraphLimit300 {MAX_NODES = 50};
typedef unsigned int Element300;
Element300 adjacencyMatrix[MAX_NODES][MAX_NODES];
Element300 distanceArray[MAX_NODES];
bool visitedSet[MAX_NODES];
int numberNodes;

Here is my current implementation of the algorithm: int startNode; int visited;

unsigned int smallest = UINT_MAX;
do
{
    startNode = getStartNode300();
    setVisitedSet300();
    smallest = UINT_MAX;
    visitedSet[startNode] = true;
    for (int i = 0; i < numberNodes; i++)
    {
        distanceArray[i] = adjacencyMatrix[startNode][i];
    }
    for (int i = 0; i < numberNodes - 1; i++)   
    {
        for (int v = 0; v < numberNodes; v++)
        {
            if (visitedSet[v] == false)
            {
                if (distanceArray[v] < smallest)
                {
                    smallest = distanceArray[v];
                    visited = v;
                }
            }
        }
        visitedSet[visited] = true;
        for (int w = 0; w < numberNodes; w++)
        {
            if (visitedSet[w] == false)
            {
                distanceArray[w] = min(distanceArray[w], distanceArray[visited] + adjacencyMatrix[visited][w]);
            }
        }
    }

On this particular for loop where it should do the certain math to find the min between values at a certain index where the nodes are false and store the min in that index. What I found is that after it chooses the smallest value in distaceArray and set it to true(which is 3 if I start at 1 using the data file below, Which is correct.).

    for (int w = 0; w < numberNodes; w++)
        {
            if (visitedSet[w] == false)
            {
                distanceArray[w] = min(distanceArray[w], distanceArray[visited] + adjacencyMatrix[visited][w]);
            }
        }

It uses the nodes '0' and '2' as of this particular iteration is the nodes that are false. And does the math for times and stores them in the wrong array.

I am using this data set that stores the numbers in adjacencyMatrix correctly.

0           5          10          4294967295
4294967295  0          4294967295  3
4294967295  7          0           4294967295
4294967295  4294967295 4           0

The correct output is:

Distance[0] =4294967295
Distance[1] =0 //Which is the node that I choose to start with
Distance[2] =7
Distance[3] =3

What I am getting is:

Distance[0] =3
Distance[1] =0
Distance[2] =3
Distance[3] =3

I have done this process by hand to confirm that the correct output that I should be getting is true and it IS.

Updated if:

if (visitedSet[w] == false && adjacencyMatrix[visited][w] != UINT_MAX)
                {
                    distanceArray[w] = min(distanceArray[w], distanceArray[visited] + adjacencyMatrix[visited][w]);
                }

Answer 1

The problem here is again, the fact that you shall only consider edges which exist, that is adjacencyMatrix[visited][w]!=UINT_MAX .

If you don't exclude these edges, distanceArray[visited] + adjacencyMatrix[visited][w] will overflow and the min() will not return the result that you expect.

You can solve this by changing this line:

if (visitedSet[w] == false && adjacencyMatrix[visited][w]!=UINT_MAX ) 

Edit:

There is indeed another problem hidden in your nested for loops. The first inner for loop looks each time for the shortest subpath to expland. Unfortuantely, you didn't reset smallest , so that it starts with the smalest value of the previous iteration.

Update the looping as follows and you'll get your explected result:

for (int i = 0; i < numberNodes - 1; i++)   
{
    smallest = UINT_MAX; // !!!!!!!!!!!!!!!!!!!!!!!
    for (int v = 0; v < numberNodes; v++) 
    {
        ...
    }
    ...
}