设计一个长沙地铁线路查询系统，为长沙地铁乘客咨询从任一个站点到另一个站点之间的最短路径问题。基本要求： （1）对地铁站点信息(站点名、站点间的里程)进行编辑：具备添加、修改、删除功能； （2）咨询以用户和计算机对话方式进行，要注意人机交互的屏幕界面。由用户选择输入起点、终点，输出信息：乘客从起点、终点经过的每一地铁站点。 （3）主程序可以有系统界面、菜单；也可用命令提示方式；选择功能模块执行，要求在程序运行过程中可以反复操作。并提供完整的可运行的C语言代码

这是一个较为复杂的问题，需要设计数据库、算法和界面等多个方面。以下是一个简单的实现思路，供参考。

1. 数据库设计：创建两个表格，一个是站点信息表格，包括站点ID、站点名、经度、纬度等信息；另一个是站点间里程表格，包括起始站点ID、终点站点ID、里程、时间等信息。

2. 算法设计：采用Dijkstra算法求最短路径。首先将所有站点设为未访问状态，起点站点设为已访问状态。然后遍历与起点站点相邻的站点，更新它们与起点站点的距离和路径，同时将其标记为已访问状态。接着选取未访问过的距离最小的站点，重复上述过程，直到终点站点被标记为已访问状态或者所有站点都被访问过。

3. 界面设计：可以采用命令行界面或者图形界面。命令行界面可以通过scanf和printf函数实现，图形界面可以采用QT或者MFC等UI框架。

以下是一个简单的C语言代码实现，仅供参考：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX_STATION_NUM 100
#define MAX_STATION_NAME_LEN 20
#define INF 0x3f3f3f3f

typedef struct {
    int id;
    char name[MAX_STATION_NAME_LEN];
    double longitude, latitude;
} Station;

typedef struct {
    int start, end;
    double distance, time;
} Distance;

Station stations[MAX_STATION_NUM];
Distance distances[MAX_STATION_NUM * MAX_STATION_NUM];
int station_num = 0, distance_num = 0;

void add_station() {
    printf("Please enter station name: ");
    scanf("%s", stations[station_num].name);
    printf("Please enter station longitude and latitude: ");
    scanf("%lf%lf", &stations[station_num].longitude, &stations[station_num].latitude);
    stations[station_num].id = station_num;
    station_num++;
}

void modify_station() {
    int id;
    printf("Please enter station id: ");
    scanf("%d", &id);
    printf("Please enter new station name: ");
    scanf("%s", stations[id].name);
    printf("Please enter new station longitude and latitude: ");
    scanf("%lf%lf", &stations[id].longitude, &stations[id].latitude);
}

void delete_station() {
    int id;
    printf("Please enter station id: ");
    scanf("%d", &id);
    // 删除站点
    for (int i = id; i < station_num - 1; i++) {
        stations[i] = stations[i + 1];
        stations[i].id--;
    }
    station_num--;
    // 删除距离
    for (int i = 0; i < distance_num; i++) {
        if (distances[i].start == id || distances[i].end == id) {
            for (int j = i; j < distance_num - 1; j++) {
                distances[j] = distances[j + 1];
            }
            distance_num--;
            i--;
        } else if (distances[i].start > id) {
            distances[i].start--;
        } else if (distances[i].end > id) {
            distances[i].end--;
        }
    }
}

void add_distance() {
    int start, end;
    double distance, time;
    printf("Please enter start station id, end station id, distance and time: ");
    scanf("%d%d%lf%lf", &start, &end, &distance, &time);
    distances[distance_num].start = start;
    distances[distance_num].end = end;
    distances[distance_num].distance = distance;
    distances[distance_num].time = time;
    distance_num++;
}

void modify_distance() {
    int start, end;
    printf("Please enter start station id and end station id: ");
    scanf("%d%d", &start, &end);
    for (int i = 0; i < distance_num; i++) {
        if (distances[i].start == start && distances[i].end == end) {
            printf("Please enter new distance and time: ");
            scanf("%lf%lf", &distances[i].distance, &distances[i].time);
            break;
        }
    }
}

void delete_distance() {
    int start, end;
    printf("Please enter start station id and end station id: ");
    scanf("%d%d", &start, &end);
    for (int i = 0; i < distance_num; i++) {
        if (distances[i].start == start && distances[i].end == end) {
            for (int j = i; j < distance_num - 1; j++) {
                distances[j] = distances[j + 1];
            }
            distance_num--;
            break;
        }
    }
}

void print_stations() {
    printf("id name longitude latitude\n");
    for (int i = 0; i < station_num; i++) {
        printf("%2d %s %lf %lf\n", stations[i].id, stations[i].name, stations[i].longitude, stations[i].latitude);
    }
}

void print_distances() {
    printf("start end distance time\n");
    for (int i = 0; i < distance_num; i++) {
        printf("%4d %3d %9lf %9lf\n", distances[i].start, distances[i].end, distances[i].distance, distances[i].time);
    }
}

void dijkstra(int start, int end) {
    int visited[MAX_STATION_NUM], prev[MAX_STATION_NUM];
    double distance[MAX_STATION_NUM];
    memset(visited, 0, sizeof(visited));
    memset(prev, -1, sizeof(prev));
    for (int i = 0; i < station_num; i++) {
        distance[i] = INF;
    }
    distance[start] = 0;
    while (!visited[end]) {
        // 找到未访问过的距离最小的站点
        int min_distance = INF, current = -1;
        for (int i = 0; i < station_num; i++) {
            if (!visited[i] && distance[i] < min_distance) {
                min_distance = distance[i];
                current = i;
            }
        }
        if (current == -1) {
            break;
        }
        visited[current] = 1;
        // 更新相邻站点的距离和路径
        for (int i = 0; i < distance_num; i++) {
            int start_id = distances[i].start, end_id = distances[i].end;
            if (start_id == current && !visited[end_id]) {
                double new_distance = distance[current] + distances[i].distance;
                if (new_distance < distance[end_id]) {
                    distance[end_id] = new_distance;
                    prev[end_id] = current;
                }
            }
            if (end_id == current && !visited[start_id]) {
                double new_distance = distance[current] + distances[i].distance;
                if (new_distance < distance[start_id]) {
                    distance[start_id] = new_distance;
                    prev[start_id] = current;
                }
            }
        }
    }
    // 输出路径
    int path[MAX_STATION_NUM], path_len = 0;
    int current = end;
    while (current != -1) {
        path[path_len++] = current;
        current = prev[current];
    }
    printf("Path: ");
    for (int i = path_len - 1; i >= 0; i--) {
        printf("%s", stations[path[i]].name);
        if (i > 0) {
            printf("->");
        }
    }
    printf("\nDistance: %lf km\n", distance[end]);
}

int main() {
    int choice = -1;
    while (choice != 0) {
        printf("1. Add station\n");
        printf("2. Modify station\n");
        printf("3. Delete station\n");
        printf("4. Add distance\n");
        printf("5. Modify distance\n");
        printf("6. Delete distance\n");
        printf("7. Print stations\n");
        printf("8. Print distances\n");
        printf("9. Find shortest path\n");
        printf("0. Exit\n");
        printf("Please enter your choice: ");
        scanf("%d", &choice);
        switch (choice) {
            case 1: add_station(); break;
            case 2: modify_station(); break;
            case 3: delete_station(); break;
            case 4: add_distance(); break;
            case 5: modify_distance(); break;
            case 6: delete_distance(); break;
            case 7: print_stations(); break;
            case 8: print_distances(); break;
            case 9: {
                int start, end;
                printf("Please enter start station id and end station id: ");
                scanf("%d%d", &start, &end);
                dijkstra(start, end);
                break;
            }
            case 0: break;
            default: printf("Invalid choice!\n"); break;
        }
    }
    return 0;
}