Question

我编写了有关实现Prim's Algorithm的代码，并构建了从顶点1开始的最小生成树。

以下是输入格式：

第一行是案件数。

每种情况都以顶点数开头。

假设我这样输入：

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

这意味着我有2个测试用例，而'4'意味着有4行顶点。

示例：

0,1,0,4

1,0,3,2

0,3,0,5

4,2,5,0

会是这样

  |0||1||2||3| 
0| 0  1  0  4
1| 1  0  3  2 
2| 0  3  0  5
3| 4  2  5  0

0到4需要4个距离，2-2需要3个距离，等等

第一个输出是正确的

0-1 1
1-2 3
1-3 2

但是第二个输出也与第一个输出相同，这意味着错误

0-1 1
1-2 3
1-3 2

这是我的代码

#include <stdio.h>
#include <limits.h>
#include<stdbool.h>
// Number of vertices in the graph
#define V 100

// A utility function to find the vertex with
// minimum key value, from the set of vertices
// not yet included in MST
int minKey(int key[], bool mstSet[])
{
// Initialize min value
int min = INT_MAX, min_index;
int v;
for (v = 0; v < V; v++)
    if (mstSet[v] == false && key[v] < min)
        min = key[v], min_index = v;

return min_index;
}

// A utility function to print the
// constructed MST stored in parent[]
int printMST(int parent[], int n, int graph[V][V])
{
int i;
char front1;
char back2;

//printf("Edge \tWeight\n");
for (i = 1; i < V; i++)
    if(graph[i][parent[i]]!=0)
    {
        front1 = parent[i];
        front1 += 16;
        back2 = i;
        back2 +=16;
        printf("%d-%d %d \n", parent[i], i, graph[i][parent[i]]);
    }

    else
        break;
}

// Function to construct and print MST for
// a graph represented using adjacency
// matrix representation
void primMST(int graph[V][V])
{
int i,count,v;
// Array to store constructed MST
int parent[V];
// Key values used to pick minimum weight edge in cut
int key[V];
// To represent set of vertices not yet included in MST
bool mstSet[V];

// Initialize all keys as INFINITE
for (i = 0; i < V; i++)
    key[i] = INT_MAX, mstSet[i] = false;

// Always include first 1st vertex in MST.
// Make key 0 so that this vertex is picked as first vertex.
key[0] = 0;
parent[0] = -1; // First node is always root of MST

// The MST will have V vertices
for (count = 0; count < V-1; count++)
{
    // Pick the minimum key vertex from the
    // set of vertices not yet included in MST
    int u = minKey(key, mstSet);

    // Add the picked vertex to the MST Set
    mstSet[u] = true;

    // Update key value and parent index of
    // the adjacent vertices of the picked vertex.
    // Consider only those vertices which are not
    // yet included in MST
    for (v = 0; v < V; v++)

        // graph[u][v] is non zero only for adjacent vertices of m
        // mstSet[v] is false for vertices not yet included in MST
        // Update the key only if graph[u][v] is smaller than key[v]
        if (graph[u][v] && mstSet[v] == false && graph[u][v] < key[v])
            parent[v] = u, key[v] = graph[u][v];
}

// print the constructed MST
printMST(parent, V, graph);
}

int main()
{

printf("%c",one1);
int i,j,limit1,limit2;
int column_a=0;
int row_a=0;
char datawithco[1000];
char *pch;
int graph[V][V];

scanf("%d",&limit1);

for(i=0; i<limit1; i++)
{
    scanf("%d",&limit2);
    for(j=0; j<limit2; j++)
    {
        scanf("%s",datawithco);
        pch = strtok (datawithco,",");
        while (pch != NULL)
        {
            //printf ("%s\n",pch);
            graph[row_a][column_a] = atoi(pch);
            column_a++;
            pch = strtok (NULL, ",");
        }
        column_a=0;
        row_a++;
    }

    primMST(graph);
    graph[row_a][column_a] = '\0';
}

return 0;
}

第二个输出应该是

Answer 1

完成每种情况的MST后，您无需重置row_a变量。

for(i=0; i<limit1; i++)
{
    scanf("%d",&limit2);
    for(j=0; j<limit2; j++)
    {
        scanf("%s",datawithco);
        pch = strtok (datawithco,",");
        while (pch != NULL)
        {
            //printf ("%s\n",pch);
            graph[row_a][column_a] = atoi(pch);
            column_a++;
            pch = strtok (NULL, ",");
        }
        column_a=0;
        row_a++;
    }

    primMST(graph);
    graph[row_a][column_a] = '\0';  
    row_a=0; //<---added
}

此外，您在每种情况下都不会重设graph。对于您提供的这些特殊情况，这很好，因为第二种情况下的顶点数大于第一种情况下的顶点数，因此第二种情况下的像元将覆盖第一种情况下的像元，否则前一种情况留下的单元格将被视为有效单元格，这显然是错误的。因此，您应该将图形重置添加到primMST()函数中，或在每种情况的开始处添加

清除C中的数组数据（Prim算法）

1 个答案: