How to solve bad alloc() runtime error?

Question

I am getting the std::bad alloc() exception in a code I have written. According to other answers on SO, I should free the dynamically allocated memory but the exception remains. Any leads on how I can solve it?

I am attaching the function where the error comes.

int count(int *S, int m, int n ) { int i, j, x, y;

// We need n+1 rows as the table is consturcted in bottom up manner using 
// the base case 0 value case (n = 0)
int **table=new int*[n+1];
for(int q=0;q< n+1;q++)
  table[q] = new int[m];

// Fill the enteries for 0 value case (n = 0)
for (i=0; i<m; i++)
    table[0][i] = 1;

// Fill rest of the table enteries in bottom up manner  
for (i = 1; i < n+1; i++)
{
    for (j = 0; j < m; j++)
    {
        // Count of solutions including S[j]
        x = (i-S[j] >= 0)? table[i - S[j]][j]: 0;

        // Count of solutions excluding S[j]
        y = (j >= 1)? table[i][j-1]: 0;

        // total count
        table[i][j] = x + y;
    }
}
int answer = table[n][m-1];
delete[] table;
return answer; }

I am basically trying to solve the coin exchange problem. n can be as big as 10^9.

Your code also leaks memory. Use vectors to avoid memory leaks. — Neil Kirk, Sep 27 '14 at 14:04
Oh yes. But there seems to no other way. If I do not take the DP solution, I will exceed the time limit. For the DP solution I need this much space. Any other way to solve the coin change problem? — TheBlueNotebook, Sep 27 '14 at 14:05
I am compiling on 64-bit, but the code eventually gets submitted to an online compiler. — TheBlueNotebook, Sep 27 '14 at 14:05
Thank you user1754322. Changing that statement didn't take care of the runtime error however. — TheBlueNotebook, Sep 27 '14 at 14:07
Btw, I guess S contains the value of each coin, m is the number of coins and n might be the quantity. Is that right? — tuket, Sep 27 '14 at 14:09

score 2 · Answer 1 · answered Sep 27 '14 at 14:05

2

Notice when you allocate table you do it in two steps. You allocate table and then each element of table. To release all the memory you must also use two steps, each table element and finally table itself.

Change your cleanup to something like:

for(int q=0;q< n+1;q++) {
  delete[] table[q];
}
delete[] table;

...or just use std::vector and avoid manual memory management.

answered Sep 27 '14 at 14:05

Blastfurnace

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It doesn't solve the runtime error I am getting when n = 1000000000, m = 5. – TheBlueNotebook Sep 27 '14 at 14:10
@TheBlueNotebook: It sounds like you need to find a different algorithm. I can delete this answer if your actual problem isn't a memory leak. – Blastfurnace Sep 27 '14 at 14:13
Okay. My code works for smaller inputs. It's only when larger inputs are given that the code fails. – TheBlueNotebook Sep 27 '14 at 14:19

How to solve bad alloc() runtime error?

1 Answers1