所以我正在尝试用 C++ 编写 Dijkstra 的最短路径算法。出于某种原因,它没有正确地计算距离...
这是我到目前为止的代码。您可以忽略我将路径复制到堆栈的部分,因为我知道它还没有完成。我哪里出错了?
#include <fstream>
#include "matrix.h"
#include <list> // STL container
using namespace std;
//---------------------------------------------------------------------------
const int INFIN = 100000;
const int size = 8;
double a[] = {
0, 0, 5, 0, 0, 2, 3, 0, //length matrix ( #9, page 276)
4, 0, 6, 0, 7, 0, 5, 0,
0, 3, 0, 9, 2, 6, 0, 7,
3, 0, 2, 0, 1, 0, 7, 6,
0, 5, 0, 1, 0, 0, 4, 0,
0, 0, 2, 0, 8, 0, 9, 0,
1, 2, 3, 0, 0, 6, 0, 0,
5, 0, 8, 0, 2, 0, 9, 0
};
// Global declarations for L Matrix and begin and end node
Matrix L(size,size,a); //length matrix
int begin, end;
void path(long* D, int* P); //function prototype for shortest path algorithm
Matrix Warshall(Matrix M);
void main()
{
int i, u;
long D [size+1]; //distance functions
int P [size+1]; //prior vertices in path
cout << "\nLength Matrix: " << L;
cout << "\nPaths that exist:" << Warshall(L);
for (i=1; i <= size; i++) {
D[i] = INFIN; //initialize distance functions
P[i] = 0;
}
cout << "\nFind distance from vertex #";
cin >> begin;
cout << " to vertex #";
cin >> end;
if (begin == end) exit(1);
if (begin < 0 || end < 0) exit(1);
if (begin > size || end > size) exit(1);
path(D,P);
cout << "\nShortest distance from \nvertex #"
<< begin << " to vertex #"
<< end << " is " << D[end];
// u = end;
list<int> stack; // work path backwards
while (1) {
stack.push_front(end);
stack.push_front(begin);
break;
}
cout << "\nusing path:\n";
cout << "\t" << stack.front();
stack.pop_front();
while (stack.size()) {
cout << " -> " << stack.front();
stack.pop_front();
}
getch();
}
void path(long* D, int* P) {
int i, u, dist;
int U[size+1];
for (i=1; i <= size; i++)
U[i] = 0;
U[begin] = 1; // add first vertex;
D[begin] = 0;
u = begin;
do { // until find end vertex
for (i = 1; i <= size; i++) {
dist = L.element(u,i); // distance from u to i
if( D[u] + dist < D[i]) {
D[i] = D[u] + dist;
P[i] = u;
}
}
dist = 38000; // reset distance value to large value
int min;
for(i = 1; i <= size; i++) {
if(L.element(u,i) != 0) {
if(L.element(u,i) < dist && U[i] != 1) {
dist = L.element(u,i);
min = i;
}
}
}
u = min;
U[u] = 1;
cout << "Min is " << min << endl;
} while (u != end);
}
最佳答案
if( D[u] + dist < D[i]) {
D[i] = D[u] + dist;
P[i] = u;
}
应该是
if( D[u] + dist < D[i] && dist != 0) {
D[i] = D[u] + dist;
P[i] = u;
}
关于c++ - Dijkstra的最短路径算法问题,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/8410579/