sdut2139图结构练习——BFS——从起始点到目标点的最短步数

http://acm.sdut.edu.cn/sdutoj/problem.php?action=showproblem&problemid=2139

BFS 借助队列 将节点的邻接点依次存入队中

View Code

 1 #include <stdio.h>

 2 #include <stdlib.h>

 3 #include<string.h>

 4 int k[1001][1001],f[1001],n,m,p = 0,w;

 5 typedef struct node

 6 {

 7     int num,y;

 8 }st;

 9 st q[1001];

10 void inque(int x)

11 {

12     p++;

13     q[p].y = x;

14     f[x] = 1;

15 }

16 int main()

17 {

18     int i,j,a,b;

19     while(scanf("%d%d", &n, &m)!=EOF)

20     {

21         memset(k,0,sizeof(k));

22         memset(f,0,sizeof(f));

23         memset(q,0,sizeof(q));

24         p = 0;

25         int flag = 0;

26         for(i = 1 ; i <= m ; i++)

27         {

28             scanf("%d%d", &a, &b);

29             k[a][b] = 1;

30         }

31         inque(n);

32         q[p].num = 0;

33         w = 0;

34         do

35         {

36             w++;

37             for(i = 1 ; i <= n ; i++)

38             {

39                 if(k[q[w].y][i] == 1&&f[i] == 0)

40                 {

41                     inque(i);

42                     q[p].num = q[w].num+1;

43                     if(i == 1)

44                     {

45                         flag = 1;

46                         break;

47                     }

48                 }

49             }

50             if(flag == 1)

51             break;

52         }while(p!=w);

53         if(flag == 1)

54         printf("%d\n",q[p].num);

55         else

56         printf("NO\n");

57     }

58     return 0;

59 }