Adding numbers in array in a specific order

Need to create a code for the following statement:

let a=[1 3 5 6 6 7 7 7] , b=[81 122 245 329 656 790 850 1023]

c=[1 1 1 2 3] where c is showing how many times a unique value of a has been repeated e.g. '1' is repeated '1' time, '6' is repeated '2' times and so on.

Now what I need to do is to create d such that if 1st index of c is 1 then assign 1st index value of b to d and if 1st index of c is 2 then assign 1st and 2nd index value of b to d.

In short what I need is d which will have value d=[81 122 245 329+656 790+850+1023].

Will appreciate your help:D

Answer 1

[Stephen23]

>> [~,~,X] = unique(a);
>> d = accumarray(X(:),b(:))
d =
     81
    122
    245
    985
   2663

[Raza Hassan]

Thanks alot. worked just fine, only thing is that I was hoping for a code rather than a built-in command to get the required result. Hope you can help me in this regard.

[Stephen23]

>> [~,~,x] = unique(a);
>> d = zeros(1,max(x));
>> for k = 1:numel(b), d(x(k)) = d(x(k)) + b(k); end
>> d
d =
          81         122         245         985        2663

[Raza Hassan]

Thank you very much.