Q:

Segmentation fault with recursion

I'm trying to write C++ code for solving house-robber problem. 
But my recursion doesn't work, I'm getting Segmentation fault.
Can't understand what's wrong. Please, take a look
int award(vector<int>& nums, int n, vector<int>& sum)
{
    if (n == 0) sum[0] = 0;
    if (n == 1) sum[1] = nums[0];
    if (n > 1) 
    {
        if ((sum[n-1]) < 0) sum[n-1] = award(nums,n-1,sum);
        if ((sum[n-2]) < 0) sum[n-2] = award(nums,n-2,sum);
        sum[n] = max(sum[n-2] + nums[n-1], sum[n-1]);
    }
    int ans = sum[n];
    return ans;
}

int main() 
{
    vector<int> nums;
    vector<int> sum (100); 
    int a;
    int i = 0;
    while (cin>>a)
    {
        nums[i] = a;
        i++;
    }
    int n = nums.size();
    for(int i = 0; i <= n; i++)
    {
        sum[i] = -1;
    }
    cout<<award(nums,n, sum);
}

A:

Let n = nums.size(). One problem is that your for loop is running from 0 to n, which is actually n+1 integers in a collection of size n. So one of them is out-of-range(and it is nums[n]).
An example: If n = 3, then 0,1,2,3 is a collection of 4 integers not 3.

