以下是我的程序的完整代码。 dijkstra函数有问题，而当我使用大于18的顶点id时，它会保持无限循环。我尝试了不同的组合，到目前为止没有看到任何问题，除了使用大于18的数字。如果你想自己编译，我也添加了样本“city_list.txt”和“weighted_list.txt”。
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define CITYLIST "city_list.txt"
#define WEIGHTLIST "weight_list.txt"
#define INFINITE 32700
#define MAXV 100
void editfile(FILE *fp);
const char *readLine(FILE *fp);
int citycode(char *string, char **cities, int vertices);
int dijkstra(int weight[MAXV][MAXV], int source, int destination, char **cities, int v);
int menu() {
printf("1. Shortest distance between point A and point B\n");
printf("2. Shortest distance to all points from point A\n");
printf("3. List of city codes\n");
printf("0. Exit\n");
int choice;
scanf("%d", &choice);
return choice;
}
int main() {
FILE *fp;
fp = fopen(CITYLIST, "r+");
editfile(fp);
char *cities[MAXV]; // To store name of the cities
char buffer[100];
memset(buffer, '\0', sizeof(buffer));
int intbuffer;
int vertices = 0; // Number of vertices
readLine(fp); // Pass the first line
/** Read city names from city_list.txt and save them into
*cities[100] array. Find the number of vertices */
while(1) {
if( fscanf(fp, "%s %d", buffer, &intbuffer) < 0 )
break;
int i = 0;
for(i = 0; buffer[i] != '\0'; i++) {
// Count inside buffer
}
cities[vertices] = (char *)malloc(i+1);
memset(cities[vertices], '\0', sizeof(*cities[vertices]));
strcpy(cities[vertices], buffer);
vertices++;
}
fclose(fp);
fp = fopen(WEIGHTLIST, "r+");
editfile(fp);
readLine(fp); // Pass the first line
int weight[MAXV][MAXV], i, j;
for(i = 0; i < MAXV; i++)
for(j = 0; j < MAXV; j++)
weight[i][j] = INFINITE;
char buffer2[100];
for(i = 0; i < vertices; i++) {
memset(buffer, '\0', sizeof(buffer));
memset(buffer2, '\0', sizeof(buffer2));
fscanf(fp, "%s %s %d", buffer, buffer2, &intbuffer);
int c1, c2;
c1 = citycode(buffer, cities, vertices);
c2 = citycode(buffer2, cities, vertices);
if(c1 == -1 || c2 == -1)
return -1;
weight[c1][c2] = intbuffer;
weight[c2][c1] = intbuffer;
}
int choice = menu();
while(choice != 0) {
if(choice == 1) {
choice = -1;
int p1, p2;
printf("Point A: ");
scanf("%d", &p1);
printf("Point B: ");
scanf("%d", &p2);
printf("\n***************\n");
dijkstra(weight, p1, p2, cities, vertices);
printf("***************\n\n");
} else if (choice == 2) {
choice = -1;
int p1;
printf("Point A: ");
scanf("%d", &p1);
int i;
printf("\n***************\n");
for(i = 0; i < vertices; i++)
if(p1 != i)
dijkstra(weight, p1, i, cities, vertices);
printf("***************\n\n");
} else if (choice == 3) {
choice = -1;
int i;
printf("\n***************\n");
for(i = 0; i < vertices; i++)
printf("%d. %s\n", i, cities[i]);
printf("***************\n\n");
}
choice = menu();
}
return 0;
}
void editfile(FILE *fp) {
while(1) {
char ch = fgetc(fp);
if(ch == '-') {
fseek(fp, ftell(fp)-1, SEEK_SET);
fputc(' ', fp);
fseek(fp, ftell(fp)-1, SEEK_SET);
}
if(ch == EOF)
break;
}
fseek(fp, 0, SEEK_SET);
}
const char *readLine(FILE *fp) {
int maxlinelength = 32;
char *line = (char *)malloc(sizeof(char) * maxlinelength);
char ch = getc(fp);
int counter = 0;
while( ch != '\n' && ch != EOF ) {
if(counter == maxlinelength) {
maxlinelength += 32;
line = realloc(line, maxlinelength);
}
line[counter] = ch;
counter++;
ch = getc(fp);
}
line[counter] = '\0'; // Add null terminator
realloc(line, counter + 1); // Get rid of extra space
return line;
}
int citycode(char *string, char **cities, int vertices) {
int i;
for(i = 0; i < vertices; i++) {
if( strcmp(string, cities[i]) == 0 )
return i;
}
return -1;
}
int dijkstra(int weight[MAXV][MAXV], int source, int destination, char **cities, int v) {
int distance[MAXV], previous[MAXV], dist, i, minid, min, path[100], p;
int selected[MAXV] = {0};
for(i = 0; i < v; i++) {
distance[i] = INFINITE;
previous[i] = -1;
}
selected[source] = 1; // Source is selected
distance[source] = 0; // Source to source distance zero
while( selected[destination] == 0 ) {
min = INFINITE;
minid = 0;
for(i = 0; i < v; i++) {
dist = distance[source] + weight[source][i];
printf("weight[%d][%d]: %d\n", source, i, weight[source][i]);
if( dist < distance[i] && selected[i] == 0 ) {
distance[i] = dist;
previous[i] = source;
} else if ( min > distance[i] && selected[i] == 0 ) {
min = distance[i];
if(i == 0)
minid = source;
else
minid = i;
}
}
source = minid;
selected[source] = 1;
}
source = destination;
p = 0;
while( source != -1 ) {
path[p] = source;
source = previous[source];
p++;
}
printf("\n---\n");
for(i = p-1; i > -1; i--) {
if(i == 0)
printf("%s", cities[path[i]]);
else
printf("%s -> ", cities[path[i]]);
}
printf("\nShortest distance: %d\n---\n\n", distance[destination]);
return distance[destination];
}
city_list.txt
City-Code
AAA-1
BBB-2
CCC-3
DDD-4
EEE-5
FFF-6
GGG-7
HHH-8
III-9
JJJ-10
KKK-11
LLL-12
MMM-13
NNN-14
OOO-15
PPP-16
RRR-17
SSS-18
TTT-19
UUU-20
WWW-21
XXX-22
ZZZ-23
weight_list.txt
City1-City2-Distance
AAA-BBB-124
AAA-CCC-123
AAA-DDD-432
AAA-EEE-653
AAA-FFF-12
BBB-CCC-54
BBB-WWW-325
BBB-XXX-146
CCC-PPP-95
CCC-RRR-69
CCC-SSS-124
DDD-JJJ-642
DDD-SSS-5
DDD-XXX-18
DDD-RRR-301
DDD-HHH-13
EEE-KKK-567
EEE-LLL-120
EEE-MMM-400
EEE-NNN-123
EEE-OOO-542
EEE-PPP-51
XXX-SSS-49
XXX-WWW-39
答案 0 :(得分：0)
当没有路由时，您的算法实现会卡住。从算法的主循环中没有退出条件。
如果您对城市进行了正确编号，那么您可能已经看到了 - 可能 - 正如您现在的城市列表一样，那里的数字与实际使用的数字不对应！请注意，您的路线列表中没有边缘GGG或ZZZ。
修复算法的一种方法是将此显式子句添加到循环中。例如：
// no vertex actually can have index v, so we can use it as a deadlock condition
while( selected[destination] == 0 && source != v) {
min = INFINITE;
minid = v;
printf("minid = %d\n", minid);
for(i = 0; i < v; i++) {
dist = distance[source] + weight[source][i];
printf("weight[%d][%d]: %d\n", source, i, weight[source][i]);
if( dist < distance[i] && selected[i] == 0 ) {
distance[i] = dist;
previous[i] = source;
}
if ( min > distance[i] && selected[i] == 0 ) {
min = distance[i];
minid = i;
}
}
selected[source] = 1;
source = minid;
getc(stdin);
}
if(selected[destination] == 0 && source == v)
{
printf("\nThere is no route!\n");
return distance[destination]; // will be INFINITE
}