The first part of this sentence contradicts the second part in two ways: 'less than' vs. '>=', and 'range of b1' vs. 'b2.range'.A bomb b1 is in destruction range of another bomb b2 if distance of b2 from the perimeter of b1 is less than the range of b1. (i.e. b2.range + b1.radius + b2.radius >= Distance(b1.center, b2.center))
I had a hard time understanding this sentence, but eventually I think it means: 'A bomb in the sequence should not set off another bomb that appears later in the sequence'. Correct, but unnecessary: how could you manually set off a bomb that has already exploded?The ith bomb in the sequence should not result explosion of the jth bomb where j > i.
A specification of the input ranges would have been nice. Even when all co-ordinates, radiusses and ranges are limited to 32-bit signed integers, some intermediate calculations could exeed the range of 64-bit integers (when calculating the square distance).
I guessed that the bombs where numbered from zero in the order given in the input, which turned out to be correct. But why not spend one more sentence in the description to take away all doubts?
Again: A very nice and original problem, but I would strongly advise the problemsetter to improve the description and have it replaced.