ダイクストラ法(2)

昨日のダイクストラ法を C でやってみた。

#include
#include
#include

#define N 6

typedef struct edge {
   int dest;
    int cost;
} Edge;

typedef struct node {
    Edge *edges[N];
    int edge_num;
    bool done;
    int cost;
    int from;
} Node;

void MakeEdge(Node *nodes[], int a, int b, int cost);
void PrintRoute(Node *nodes[], int start, int goal);
void FreeNodes(Node *nodes[]);

int main(void)
{
    Node *nodes[N];
    Node *start_node, *n, *n2;
    Node *done_node;
    Edge *e;
    int i, j;
    int start, goal;

    // initialize graph.
    for (i = 0; i < N; i++) {
        nodes[i] = (Node *)malloc(sizeof(Node));
        nodes[i]->done = false;
        nodes[i]->cost = -1;
        nodes[i]->from = -1;
        nodes[i]->edge_num = 0;
        for (j = 0; j < N; j++) {
            nodes[i]->edges[j] = NULL;
        }
    }
    MakeEdge(nodes, 0, 1, 2);
    MakeEdge(nodes, 0, 2, 4);
    MakeEdge(nodes, 0, 3, 5);
    MakeEdge(nodes, 1, 2, 3);
    MakeEdge(nodes, 2, 3, 2);
    MakeEdge(nodes, 1, 4, 6);
    MakeEdge(nodes, 2, 4, 2);
    MakeEdge(nodes, 4, 5, 4);
    MakeEdge(nodes, 3, 5, 6);

    start = 0;
    goal = 5;

    start_node = nodes[start];
    start_node->cost = 0;
    start_node->done = true;
    for (i = 0; i < start_node->edge_num; i++) {
        e = start_node->edges[i];
        n = nodes[e->dest];
        n->cost = e->cost;
        n->from = start;
    }

    while (true) {
        done_node = NULL;
        for (i = 0; i < N; i++) {
            n = nodes[i];
            if (n->done || n->cost < 0) {
                continue;
            } else {
                for (j = 0; j < nodes[i]->edge_num; j++) {
                    e = n->edges[j];
                    n2 = nodes[e->dest];
                    if (n2->cost < 0) {
                        n2->cost = nodes[i]->cost + e->cost;
                        n2->from = i;
                    } else if (n->cost + e->cost < n2->cost) {
                        n2->cost = n->cost + e->cost;
                        n2->from = i;
                    }
                }
                if (done_node == NULL || n->cost < done_node->cost) {
                    done_node = n;
                }
            }
            done_node->done = true;
        }
        if (done_node == NULL) {
            break;
        }
    }

    printf("%d\n", nodes[goal]->cost);
    PrintRoute(nodes, start, goal);

    FreeNodes(nodes);

    return 0;
}

void MakeEdge(Node *nodes[], int a, int b, int cost)
{
    Edge *e1, *e2;

    e1 = (Edge *)malloc(sizeof(Edge));
    e1->dest = b;
    e1->cost = cost;
    nodes[a]->edges[nodes[a]->edge_num] = e1;
    nodes[a]->edge_num++;

    e2 = (Edge *)malloc(sizeof(Edge));
    e2->dest = a;
    e2->cost = cost;
    nodes[b]->edges[nodes[b]->edge_num] = e2;
    nodes[b]->edge_num++;

    return;
}

void PrintRoute(Node *nodes[], int start, int goal)
{
    int route[N];
    int hop = 0;

    route[hop] = goal;
    for (hop = 0; route[hop] != start; hop++) {
        route[hop + 1] = nodes[route[hop]]->from;
    }

    printf("%d", route[hop--]);
    for (; hop >= 0; hop--) {
        printf(" -> %d", route[hop]);
    }
    printf("\n");

    return;
}

void FreeNodes(Node *nodes[])
{
    int i, j;

    for (i = 0; i < N; i++) {
        for (j = 0; j < nodes[i]->edge_num; j++) {
            free(nodes[i]->edges[j]);
        }
        free(nodes[i]);
    }

    return;
}
[email protected] $ ./dijkstra
10
0 -> 2 -> 4 -> 5

カテゴリー: algorithm, C パーマリンク

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