图论中的sb错误集锦

　　1.floyd——jzyzoj1213　　最优乘车

　　　　策略非常简单，就是建立权值为1的边就好了，然而处理数据的时候翻了个sb错误：

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<string>
 5 using namespace std;
 6 #define MAX 510
 7 int m,n,a[510][510],queue[51000];
 8 string s[110];
 9 void work()
10 {
11     cin>>m>>n;
12     for (int i=0;i<=m;i++)
13         getline(cin,s[i]);
14     for (int i=1;i<=m;i++)
15     {
16         int len=0;
17         for (int j=0;j<s[i].size();j++)
18             if (s[i][j]!=‘ ‘)
19                 queue[++len]=s[i][j]-‘0‘;
20         for (int j=1;j<=len;j++)
21             for (int k=j+1;k<=len;k++)
22                 a[queue[j]][queue[k]]=1;
23     }
24 }
25
26 void floyd()
27 {
28     for (int k=1;k<=n;k++)
29         for (int i=1;i<=n;i++)
30             for (int j=1;j<=n;j++)
31                 if (a[i][j]>a[i][k]+a[k][j])
32                     a[i][j]=a[i][k]+a[k][j];
33 }
34 int main()
35 {
36     //freopen("add.in","r",stdin);
37     //freopen("add.out","w",stdout);
38     memset(a,10,sizeof(a));
39     work();
40     floyd();
41     if (a[1][n]>MAX)    cout<<"NO"<<endl;
42     else    cout<<a[1][n]-1<<endl;
43     return 0;
44 }

错误代码

　　　　因为读入的是string，所以当string中出现大于9的数时是无法处理的。其实正确的处理方法加一个while即可

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<string>
 5 using namespace std;
 6 #define MAX 510
 7 int m,n,a[510][510],queue[51000];
 8 string s[110];
 9 void work()
10 {
11     cin>>m>>n;
12     for (int i=0;i<=m;i++)
13         getline(cin,s[i]);
14     for (int i=1;i<=m;i++)
15     {
16         int len=0;
17         int lens=s[i].size();
18         for (int j=0;j<lens;j++)
19             if (s[i][j]!=‘ ‘)
20             {
21                 int num=0;
22                 while(s[i][j]!=‘ ‘&&j<lens)
23                 {
24                     num*=10;
25                     num+=s[i][j]-‘0‘;
26                     j++;
27                 }
28                 j--;
29                 queue[++len]=num;
30             }
31         for (int j=1;j<=len;j++)
32             for (int k=j+1;k<=len;k++)
33                 a[queue[j]][queue[k]]=1;
34     }
35 }
36
37 void floyd()
38 {
39     for (int k=1;k<=n;k++)
40         for (int i=1;i<=n;i++)
41             for (int j=1;j<=n;j++)
42                 if (a[i][j]>a[i][k]+a[k][j])
43                     a[i][j]=a[i][k]+a[k][j];
44 }
45 int main()
46 {
47     //freopen("add.in","r",stdin);
48     //freopen("add.out","w",stdout);
49     memset(a,1,sizeof(a));
50     work();
51     floyd();
52     if (a[1][n]>MAX)    cout<<"NO"<<endl;
53     else    cout<<a[1][n]-1<<endl;
54     return 0;
55 }

AC代码

　　2.floyd——jzyzoj1214　　bessie come home

　　　　floyd的模板题，啊啊啊啊为什么我做一道题就错一道题。

　　　　注意双向边还是单向边啊啊啊啊啊

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
int n,a[56][56],len;
char st,en;
void init()
{
    cin>>n;
    for (int i=1;i<=n;i++)
    {
        cin>>st>>en>>len;
        //cout<<st<<‘ ‘<<en<<‘ ‘<<len<<endl;
        int j,k;
        if (st<=‘Z‘)
            j=st-‘A‘+1;
        else
            j=st-‘a‘+27;
        if (en<=‘Z‘)
            k=en-‘A‘+1;
        else
            k=en-‘a‘+27;
        //cout<<j<<‘ ‘<<k<<endl;
        a[j][k]=min(len,a[j][k]);
    }
}

void floyd()
{
    for (int i=1;i<=52;i++)
        a[i][i]=0;
    for (int k=1;k<=52;k++)
        for (int i=1;i<=52;i++)
            for (int j=1;j<=52;j++)
                if (a[i][j]>a[i][k]+a[j][k])
                    a[i][j]=a[i][k]+a[j][k];
}

int work()
{
    int st,minn=999999999;
    for (int i=1;i<=25;i++)
        if (a[i][26]<minn)
        {
            minn=a[i][26];
            st=i;
        }
    return st;
}

int main()
{
    ios::sync_with_stdio(false);
    //freopen("add.in","r",stdin);
    //freopen("add.out","w",stdout);
    memset(a,1,sizeof(a));
    init();
    floyd();
    int ans=work();
    char answer;
    if (ans<26)
        answer=char(ans+‘A‘-1);
    else
        answer=char(ans-27+‘a‘);
    cout<<answer<<‘ ‘<<a[ans][26]<<endl;
    return 0;
}

错误代码

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 using namespace std;
 6 int n,a[56][56],len;
 7 char st,en;
 8 void init()
 9 {
10     cin>>n;
11     for (int i=1;i<=n;i++)
12     {
13         cin>>st>>en>>len;
14         //cout<<st<<‘ ‘<<en<<‘ ‘<<len<<endl;
15         int j,k;
16         if (st<=‘Z‘)
17             j=st-‘A‘+1;
18         else
19             j=st-‘a‘+27;
20         if (en<=‘Z‘)
21             k=en-‘A‘+1;
22         else
23             k=en-‘a‘+27;
24         //cout<<j<<‘ ‘<<k<<endl;
25         a[j][k]=min(len,a[j][k]);
26         a[k][j]=a[j][k];
27     }
28 }
29
30 void floyd()
31 {
32     for (int i=1;i<=52;i++)
33         a[i][i]=0;
34     for (int k=1;k<=52;k++)
35         for (int i=1;i<=52;i++)
36             for (int j=1;j<=52;j++)
37                 if (a[i][j]>a[i][k]+a[j][k])
38                     a[i][j]=a[i][k]+a[j][k];
39 }
40
41 int work()
42 {
43     int st,minn=999999999;
44     for (int i=1;i<=25;i++)
45         if (a[i][26]<minn)
46         {
47             minn=a[i][26];
48             st=i;
49         }
50     return st;
51 }
52
53 int main()
54 {
55     ios::sync_with_stdio(false);
56     //freopen("add.in","r",stdin);
57     //freopen("add.out","w",stdout);
58     memset(a,1,sizeof(a));
59     init();
60     floyd();
61     int ans=work();
62     char answer;
63     answer=char(ans+‘A‘-1);
64     cout<<answer<<‘ ‘<<a[ans][26]<<endl;
65     return 0;
66 }

AC代码