分割故障，程序工作正常

我正在实现最小生成树问题的Prim算法。程序只是工作正常，我得到所需的输出，但我收到了分割故障在结束。我检查了我的程序的错误，但程序是好的。

这里是源代码

#include <iostream>
#include <cstdio>
#define INF 1000000
#define N 5
using namespace std;
class Graph
{
    int V;
    int adj[][N];
    public:
        Graph(int,int mat[][N]);
        void primsMST();
};
Graph::Graph(int v, int mat[][N])
{
   this->V = v;
   for(int i=0; i<v; i++)
   {
       for(int j=0; j<v; j++)
           adj[i][j] = mat[i][j];
   }
}
void Graph::primsMST()
{
    int i, j;
    int key[V];     // Key Value which is used to pick minimum weight vertex
    int parent[V];  // To store Tree
    bool mstSet[V];  // Mark Vertex included in MST
    // Initialize Key Values to infinite and mstSet to false
    for(i=0; i<V; i++)
    {
        key[i]=INF;
        mstSet[i] = false;
    }
    // Initialize initial vertex
    key[0] = 0;
    parent[0] = -1;
    int minm, min_i;
    for(int k=0; k<V-1; k++)
    {
        // Get min Key from all vertices
        minm = INF;
        for(i=0; i<V; i++) {
            if(!mstSet[i] && key[i]<minm)
            {
                minm = key[i];
                min_i = i;
            }
        }
        // Include min key vertex in MST
        mstSet[min_i] = true;
        // Update key values of vertices adjacent to min vertex
        for(j=0; j<V; j++)
        {
            if( adj[min_i][j] && !mstSet[j] && adj[min_i][j] < key[j])
            {
                key[j] = adj[min_i][j];
                parent[j] = min_i;
            }
        }
    }
    for(i=0; i<V; i++)
        cout<<i<<", "<<key[i]<<", "<<parent[i]<<endl;
    // Print Minimum spanning Tree
    cout<<"EdgetWeight"<<endl;
    for(i=1; i<V; i++)
        cout<<i<<"--"<<parent[i]<<"t"<<adj[i][parent[i]]<<endl;
    cout<<endl;
}
int main()
{
    int adjmat[][N] =  {{0, 2, 0, 6, 0},
                      {2, 0, 3, 8, 5},
                      {0, 3, 0, 0, 7},
                      {6, 8, 0, 0, 9},
                      {0, 5, 7, 9, 0},
                     };
    Graph g(N, adjmat);
    g.primsMST();
    cout<<endl;
    return 0;
}

程序使用gcc version 4.7.2编译。当我运行这个程序时，我得到了图形的所需输出，但最终出现了分割错误。

$ ./primsMST
0, 0, -1
1, 2, 0
2, 3, 1
3, 6, 0
4, 5, 1
Edge    Weight
1--0    2
2--1    3
3--0    6
4--1    5
Segmentation fault

$ gdb primsMST
GNU gdb (GDB) 7.4.1-debian
Copyright (C) 2012 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /home/abhishek/myPrograms/geeksforgeeks/graphs/primsMST...done.
(gdb) set logging on
Copying output to gdb.txt.
(gdb) run
Starting program: /home/abhishek/myPrograms/geeksforgeeks/graphs/primsMST 
0, 0, -1
1, 2, 0
2, 3, 1
3, 6, 0
4, 5, 1
Edge    Weight
1--0    2
2--1    3
3--0    6
4--1    5

Program received signal SIGSEGV, Segmentation fault.
0x0000000000000002 in ?? ()
(gdb) backtrace
#0  0x0000000000000002 in ?? ()
#1  0x0000000800000003 in ?? ()
#2  0x0000000000000005 in ?? ()
#3  0x0000000000000003 in ?? ()
#4  0x0000000700000000 in ?? ()
#5  0x0000000800000006 in ?? ()
#6  0x0000000000000000 in ?? ()
(gdb) quit 

谁能解释为什么我得到这个错误?