[Subset sum problem][1]

[1]: http://www.codechef.com/CODX2014/problems/REN2013D

I could not understand the algorithm for this problem. Somone explain this code plz

```
bool isSubsetSum(int set[], int n, int sum)
{
bool subset[sum+1][n+1];
for (int i = 0; i <= n; i++)
subset[0][i] = true;
for (int i = 1; i <= sum; i++)
subset[i][0] = false;
for (int i = 1; i <= sum; i++)
{
for (int j = 1; j <= n; j++)
{
subset[i][j] = subset[i][j-1];
if (i >= set[j-1])
subset[i][j] = subset[i][j] || subset[i - set[j-1]][j-1];// ???
}
}
return subset[sum][n];
}
```