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comparing 2 columns of two files, then do substraction if 2 columns equal

Posted on 2006-06-21
2
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Last Modified: 2010-04-01
Hi experts,

Two files, file1, file2

file1
Store id          sale amt
123               100
234               200
345               300


file2
store id          sale amt
345               50
123               60
234               70

What I want to do is comparing the store id,
if (file1.store id == file2.store id)
then file1.sale amt - file2.sale amt

so the correct results should be
store id   sale increase
123         40
234         130
345         250

But I got wrong results like
store id   sale increase
123        150
234        140
345        230


I use
set<string> stores
string file1storeid=file1.store id
string file2storeid=file2.store id
stores.insert(file2storeid)
if (stores.find(file1storeid) == stores.end()))
{
file1.sale amt - file2.sale amt
}

Please help - Thanks
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Comment
Question by:justinY
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2 Comments
 
LVL 17

Accepted Solution

by:
rstaveley earned 125 total points
ID: 16964860
Try using the store id  as a key to a map.

e.g.

typedef string StoreId;
typedef double SaleAmount;
typedef map<StoreId,SaleAmount> Database;

Database db;

// Process file 2 first
while (/* read record from file */) {

    StoredId storeId = /* */;
    SaleAmount saleAmount = /* */;
    db[storeId] = saleAmount;
}

// Then process file 1
while (/* read record from file */) {

    StoredId storeId = /* */;
    SaleAmount saleAmount = /* */;
    db[storeId] -= saleAmount;  // Subtract the sale amount - database now stores the difference
}

// Then generate the report, by iterating through the database

for (Database::const_iterator itr = db.begin();itr != db.end();++itr) {

    const StoredId& storeId = itr->first;
    const SaleAmount& saleDifference = itr->second;
    cout << /* */;
}
0
 

Author Comment

by:justinY
ID: 17004970
Thank you so much. It works
0

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