6-11 Shortest Path [1]（25 分）

6-11 Shortest Path [1]（25 分）

Write a program to find the unweighted shortest distances from any vertex to a given source vertex in a digraph.

Format of functions:

void ShortestDist( LGraph Graph, int dist[], Vertex S );

where LGraph is defined as the following:

typedef struct AdjVNode *PtrToAdjVNode; 
struct AdjVNode{
    Vertex AdjV;
    PtrToAdjVNode Next;
};

typedef struct Vnode{
    PtrToAdjVNode FirstEdge;
} AdjList[MaxVertexNum];

typedef struct GNode *PtrToGNode;
struct GNode{  
    int Nv;
    int Ne;
    AdjList G;
};
typedef PtrToGNode LGraph;

The shortest distance from V to the source S is supposed to be stored in dist[V]. If V cannot be reached from S, store -1 instead.

Sample program of judge:

#include 
#include 

typedef enum {false, true} bool;
#define MaxVertexNum 10  /* maximum number of vertices */
typedef int Vertex;      /* vertices are numbered from 0 to MaxVertexNum-1 */

typedef struct AdjVNode *PtrToAdjVNode; 
struct AdjVNode{
    Vertex AdjV;
    PtrToAdjVNode Next;
};

typedef struct Vnode{
    PtrToAdjVNode FirstEdge;
} AdjList[MaxVertexNum];

typedef struct GNode *PtrToGNode;
struct GNode{  
    int Nv;
    int Ne;
    AdjList G;
};
typedef PtrToGNode LGraph;

LGraph ReadG(); /* details omitted */

void ShortestDist( LGraph Graph, int dist[], Vertex S );

int main()
{
    int dist[MaxVertexNum];
    Vertex S, V;
    LGraph G = ReadG();

    scanf("%d", &S);
    ShortestDist( G, dist, S );

    for ( V=0; VNv; V++ )
        printf("%d ", dist[V]);

    return 0;
}

/* Your function will be put here */

Sample Input (for the graph shown in the figure):

7 9
0 1
0 5
0 6
5 3
2 1
2 6
6 4
4 5
6 5
2

Sample Output:

-1 1 0 3 2 2 1

void ShortestDist(LGraph Graph, int dist[], Vertex S)
{
int Front = 0, Rear = 0;
Vertex* queue = (Vertex*)malloc(MaxVertexNum * sizeof(Vertex));
for (int i = 0; i < MaxVertexNum; i++)
queue[i] = dist[i] = -1;
queue[0] = S;
dist[S] = 0;
PtrToAdjVNode ptr;
while (Front <= Rear) {
ptr = Graph->G[queue[Front]].FirstEdge;
while (ptr != NULL) {
if (dist[ptr->AdjV] == -1) {
dist[ptr->AdjV] = dist[queue[Front]] + 1;
queue[++Rear] = ptr->AdjV;
}
ptr = ptr->Next;
}
Front++;
}
}