poj1724ROADS（BFS）

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本来想写spfa 加点什么限制什么的可能就过了 写着写着就成裸BFS了 也没优化就水过了

 1 #include <iostream>

 2 #include<cstdio>

 3 #include<cstring>

 4 #include<algorithm>

 5 #include<stdlib.h>

 6 #include<queue>

 7 using namespace std;

 8 #define N 110

 9 #define M 10010

10 #define INF 0xfffffff

11 struct node

12 {

13     int u,v,w,next,len;

14 }ed[M<<1];

15 struct mode

16 {

17     int u,sum,len;

18 };

19 int head[N],vis[N],dis[N];

20 int n,m,t,sp,ans;

21 void init()

22 {

23     t = 0;

24     memset(head,-1,sizeof(head));

25 }

26 void add(int u,int v,int w,int len)

27 {

28     ed[t].u = u;

29     ed[t].v = v;

30     ed[t].w = w;

31     ed[t].len = len;

32     ed[t].next = head[u];

33     head[u] = t++;

34 }

35 void spfa()

36 {

37     queue<mode>q;

38     mode ss,st;

39     int i;

40     for(i = 2; i <= n ; i++)

41     dis[i] = INF;

42     ss.u = 1;

43     ss.sum = 0;

44     ss.len = 0;

45     q.push(ss);

46     dis[1] = 0;

47     while(!q.empty())

48     {

49         ss = q.front();

50         q.pop();

51         int u = ss.u;

52         if(ss.len>ans)

53         continue;

54         if(u==n)

55         {

56             ans = ss.len;

57             continue;

58         }

59         for(i = head[u] ; i!=-1 ; i = ed[i].next)

60         {

61             int v = ed[i].v;

62             if(ss.sum+ed[i].w<=sp)

63             {

64                 st.len = ss.len+ed[i].len;

65                 st.u = v;

66                 st.sum = ss.sum+ed[i].w;

67                 q.push(st);

68             }

69         }

70     }

71     if(ans!=INF)

72     printf("%d\n",ans);

73     else

74     printf("-1\n");

75 }

76 int main()

77 {

78     int i,u,v,len,w;

79     while(scanf("%d",&sp)!=EOF)

80     {

81         init();

82         ans = INF;

83         scanf("%d%d",&n,&m);

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

85         {

86             scanf("%d%d%d%d",&u,&v,&len,&w);

87             add(u,v,w,len);

88         }

89         spfa();

90     }

91     return 0;

92 }

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