如何获取向量中大于0的值的索引？

Question

I have a vector of size 1 000 000. I am increasing some values at some indexes.

How to get these indexes that were increased(that are not 0). I do not want iterate through the whole vector, it will be too slow.

For example, the input is 5 1 2 1 3 1 so the vector will look like this [0, 3, 1, 1, 0, 0, 0...] , the 5 is the size of the input. And I want to get from this vector only [3,1,1] .

Another example, the input is 6 9 1 1 1 3 1 so the vector will look like this [0, 4, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, ...] , the 6 is the size of the input. And I want to get from this vector only [4, 1, 1] .

Answer 1

I have a vector of size 1 000 000. I am increasing some values at some indexes.

How to get these indexes that were increased(that are not 0). I do not want iterate through the whole vector, it will be too slow.

For example, the input is 5 1 2 1 3 1 so the vector will look like this [0, 3, 1, 1, 0, 0, 0...] , the 5 is the size of the input. And I want to get from this vector only [3,1,1] .

Another example, the input is 6 9 1 1 1 3 1 so the vector will look like this [0, 4, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, ...] , the 6 is the size of the input. And I want to get from this vector only [4, 1, 1] .

Answer 2

I have a vector of size 1 000 000. I am increasing some values at some indexes.

How to get these indexes that were increased(that are not 0). I do not want iterate through the whole vector, it will be too slow.

For example, the input is 5 1 2 1 3 1 so the vector will look like this [0, 3, 1, 1, 0, 0, 0...] , the 5 is the size of the input. And I want to get from this vector only [3,1,1] .

Another example, the input is 6 9 1 1 1 3 1 so the vector will look like this [0, 4, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, ...] , the 6 is the size of the input. And I want to get from this vector only [4, 1, 1] .