第三次：第二题

>几点说明：
>- txt文件见`matrix.txt`文件
>- 本题直接采用了上一题中输入边数的建议，具体变化见`matrix.txt`文件，而且由于老师给的题中是无向图，所以直接xy和yx赋值。

```c
#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>

int main(){
    int ** matrix;
    // read the file and get the matrix
    FILE * fp = fopen("matrix.txt", "r");
    if(fp == NULL){
        printf("Open file error !\n");
        return 0;
    }
    int size, edges;
    int x, y, value;
    int i, j;
    fscanf(fp, "%d %d", &size, &edges);
    // printf("%d, %d\n", size, edges);
    matrix = (int **)malloc(sizeof(int *) * size);
    for(i = 0; i < size; i++){
        matrix[i] = (int *)malloc(sizeof(int) * size);
        for(j = 0; j < size; j++){
            matrix[i][j] = 0;
        }
    }
    for(i = 0; i <= edges; i++){
        fscanf(fp, "%d %d %d", &x, &y, &value);
        matrix[x][y] = value;
        matrix[y][x] = value;
    }
    fclose(fp);
    // show the matrix
    for(i = 0; i < size; i++){
        for(j = 0; j < size; j++){
            printf("%d  ", matrix[i][j]);
        }
        printf("\n");
    }

// deal with it by djikstra
    int * dis = (int *)malloc(sizeof(int) * size);
    int * flag = (int *)malloc(sizeof(int) * size);
    dis[0] = 0;
    flag[0] = 1;
    for(i = 1; i < size; i++){
        if(matrix[0][i] != 0){
            dis[i] = matrix[0][i];
            flag[i] = -1;
        }
        else{
            dis[i] = 9999;
            // means infinity
            flag[i] = 0;
        }
    }
    int min, min_num;
    min = 9999;
    while(1){
        // get min
        for(i = 0; i < size; i++){
            if(flag[i] == -1){
                if(dis[i] < min){
                    min = dis[i];
                    min_num = i;
                }
            }
        }
        flag[min_num] = 1;
        // if finished
        for(i = 0; i < size; i++){
            if(flag[i] != 1){
                break;
            }
        }
        if(i == size){
            break;
        }
        // reset dis
        for(i = 0; i < size; i++){
            if(flag[i] != 1){
                if(matrix[min_num][i] != 0){
                    if((min + matrix[min_num][i]) < dis[i]){
                        dis[i] = min + matrix[min_num][i];
                        flag[i] = -1;
                    }
                }
            }
        }
        // set min to 9999 max
        min = 9999;
    }

// print the result
    printf("The result is : \n");
    for(i = 0; i < size; i++){
        printf("%d  ", dis[i]);
    }

return 0;
}
```