coin coloring pseudo-code

gistfile1.cpp

     // we have three state variables, let's initialize them:
     cur_amount = 0; // current amount of inputs
     cur_color = COLOR_UNKNOWN; // color of those inputs
     ii = inputs.begin(); // inputs iterator

     oi = outputs.begin(); //output iterator
     for (; oi != outputs.end(); ++oi) { // go through all outputs
          want_amount = oi->amount; // amount of output we're matching
          
          // eat inputs if needed
          while ((cur_amount < want_amount) // do we need more?
                 && 
                 (ii != inputs.end())) // have we reached the end?
          {   // eat input pointed to by iterator

               if (cur_amount == 0) // brand new color stripe
                    cur_color = ii->color;
               else if (cur_color != ii->color)
                    // if we already have some, we need to check whether 
                    // coins are of same color. if they are not, they are
                    // mixed
                    cur_color = COLOR_MIXED;
               
               cur_amount += ii->amount; // add to out amount
               ++ii; // and go to next input          
          }

          if (cur_amount < want_amount)
               // we could not get enough from inputs
               // transaction is invalid if sum(inputs) > sum(outputs)
               return false;     

          oi->color = cur_color; // assign color to output
          cur_amount -= oi->amount; // decrease current amount by sum we've used
     }