UVA 1592 Database(map)

Peter studies the theory of relational databases. Table in the relational database consists of values that are arranged in rows and columns.

There are different normal forms that database may adhere to. Normal forms are designed to minimize the redundancy of data in the database. For example, a database table for a library might have a row for each book and columns for book name, book author, and author's email.

If the same author wrote several books, then this representation is clearly redundant. To formally define this kind of redundancy Peter has introduced his own normal form. A table is in Peter's Normal Form (PNF) if and only if there is no pair of rows and a pair of columns such that the values in the corresponding columns are the same for both rows.

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The above table is clearly not in PNF, since values for 2rd and 3rd columns repeat in 2nd and 3rd rows. However, if we introduce unique author identifier and split this table into two tables -- one containing book name and author id, and the other containing book id, author name, and author email, then both resulting tables will be in PNF.

Given a table your task is to figure out whether it is in PNF or not.

Input 

Input contains several datasets. The first line of each dataset contains two integer numbersn and m (1n10000, 1m10), the number of rows and columns in the table. The following n lines contain table rows. Each row hasm column values separated by commas. Column values consist of ASCII characters from space (ASCII code 32) to tilde (ASCII code 126) with the exception of comma (ASCII code 44). Values are not empty and have no leading and trailing spaces. Each row has at most 80 characters (including separating commas).

Output 

For each dataset, if the table is in PNF write to the output file a single word ``YES" (without quotes). If the table is not in PNF, then write three lines. On the first line write a single word ``NO" (without quotes). On the second line write two integer row numbers r₁ andr₂ (1r₁,r₂n,r₁r₂), on the third line write two integer column numbers c₁ andc₂ (1c₁,c₂m,c1c2), so that values in columnsc₁ andc₂ are the same in rowsr₁ andr₂.

Sample Input 

3 3aj ji le*jhjuj la na_aj ji le*jh2 4jfi jai ne jiknja jei nda j3 4knja jei nda jjuj la na_ o9ojj jei nda o

Sample Output 

YES

NOYES

题意及题解源于紫书P128。

代码：

#include <iostream>#include <algorithm>#include <cstdlib>#include <map>#include <vector>using namespace std;int main(){    int n,m;    while(cin>>n>>m)    {        string s[n][m];        map<string,int> d_ma;        int cnt=0;        for(int i=0;i<n;i++)        for(int j=0;j<m;j++)        {            cin>>s[i][j];            if(!d_ma.count(s[i][j]))            {                d_ma[s[i][j]]=cnt;                cnt++;            }        }        int flag=0;        map<int,int> d_int;        for(int i=0;i<m-1;i++)        {            for(int j=i+1;j<m;j++)            {                for(int k=0;k<n;k++)                {                    if(i==0&&j==i+1&&k==0)                        d_int[d_ma[s[k][i]]]=d_ma[s[k][j]];                    else                    {                        if(d_int[d_ma[s[k][i]]]==d_ma[s[k][j]])//判断map 中是否已经存在该二元组                        {                            cout<<"YES"<<endl;                            flag=1;                            break;                        }                        else                            d_int[d_ma[s[k][i]]]=d_ma[s[k][j]];//添加新二元组                    }                }                if(flag)                    break;            }            if(flag)                break;        }        if(!flag)            cout<<"NO"<<endl;    }    return 0;}