我有以下程序,首先存储一些城市之间的直达航班,然后使用DFS查询两个城市是否通过间接航班连接。
程序在查询步骤中一直崩溃,所以我试图使用print语句找到问题,奇怪的是当执行搜索的函数中有print语句时程序不会崩溃。代码有什么问题?
(我正在使用代码:块13.12)
#include <stdio.h>
#include <stdlib.h>
#define MIN_SIZE 2
#define MAX_SIZE 10000
#define MIN_CON 1
#define FALSE 0
#define TRUE 1
//global variables
struct city** checked;
int* num_connect;
int n, found=0;
//Define a struct
struct city
{
//Declaration of struct members
int name;
struct city **connected; //array of all cities with direct flights to
};
int readCity(int n)
{
//Declaration of a variable
int city;
do
{
scanf("%d", &city);
}while(city<MIN_CON && city>n);
return city;
}
void addFlight(struct city *list, int orig, int dest)
{
//decl
int i=0;
int j=0;
//check if orig is in list
while(num_connect[i]!=0 && list[i].name!=orig)
{
i++;
}
//if it isnt add it
if (num_connect[i]==0)
{
list[i].name =orig;
list[i].connected = malloc((num_connect[i]+1)*sizeof(struct city*));
}
else
{
//reallocate memory to store additional flight connection
list[i].connected = realloc(list[i].connected, (num_connect[i]+1)*sizeof(struct city*));
}
num_connect[i]++;
//check if dest is in list
while(num_connect[j]!=0 && list[j].name!=dest)
{
j++;
}
//if it isnt add it
if (num_connect[j]==0)
{
list[j].name =dest;
list[j].connected = malloc((num_connect[j]+1)*sizeof(struct city*));
}
else
{
//reallocate memory to store additional flight connection
list[j].connected = realloc(list[j].connected, (num_connect[j]+1)*sizeof(struct city*));
}
num_connect[j]++;
//add b to a's connected and add b to a's connected
list[j].connected[num_connect[j]-1]=&list[i];
list[i].connected[num_connect[i]-1]=&list[j];
printf("JUST CONNECTED %d WITH %d\n", list[i].name, list[j].name);
}
int inChecked(struct city* c)
{
int i;
while(checked[i]!=c && i<n)
{
i++;
}
if (i==n)
{
return FALSE;
}
else
{
return TRUE;
}
}
void search_connection(struct city *list, int orig, int dest)
{
//decl
int i=0, k=0, j=0, p=0;
printf(" "); // <------------------------------------------------------------
//Find origin city in list
while(i<n && list[i].name!=orig)
{
i++;
}
//add to checked
while(checked[k]!=NULL)
{
k++;
}
checked[k]=&list[i];
//Check for 'dest' city in connected of origin
while(j<num_connect[i] && list[i].connected[j]->name!=dest)
{
j++;
}
//If-statement to determine if dest was found
if (j!=num_connect[i])
{
//Set 'found' to 1
found=1;
return;
}
else
{
//While not all connected have been checked and not found
while(p<num_connect[i] && found==0)
{
if (!inChecked(list[i].connected[p]))
{
//call method on it
search_connection(list, list[i].connected[p]->name, dest);
}
p++;
}
}
}
int main()
{
//Declaration of variables
int i, m;
int city_a, city_b, q_result;
//Read input
do
{
//printf("Enter number of cities:\n");
scanf("%d", &n);
}while(n<MIN_SIZE || n>MAX_SIZE);
//Declare an array of cities
struct city* cities;
//Allocate memory for array of 'n' cities
cities = malloc(n*sizeof(struct city)); // <---------------- FREE later!!!
//Allocate memory for array of 'n' pointers to cities
checked = calloc(n,sizeof(struct city*)); // <---------- FREE later!!!
//Allocate memory for array of 'n' integers
num_connect = calloc(n,sizeof(int)); // <------------ FREE later!!!
//Read input
do
{
//printf("Enter number of connections:\n");
scanf("%d", &m);
}while(n<MIN_SIZE || n>MAX_SIZE);
//For-loop to read connected cities
for (i=0; i<m; i++)
{
//Read two cities
city_a = readCity(n);
city_b = readCity(n);
//add flight connecting the two cities
addFlight(cities, city_a, city_b);
}
//Read connection to query
city_a = readCity(n);
city_b = readCity(n);
//Search for connection between the two cities by in-direct flight
search_connection(cities, city_a, city_b);
//Print results
if (found==1)
{
printf("Yes");
}
else
{
printf("No");
}
//Free up memory
// TO DO. . .
return 0;
}
答案 0 :(得分:2)
在inChecked()
中,您永远不会初始化i
,因此您的函数会随机运行。如果该函数返回false太多次,则稍后可能会溢出checked
数组。