Problem Statement

An equilibrium index of a sequence is an index into the sequence such that the sum of elements at lower indices is equal to the sum of elements at higher indices.

For example, in a sequence

A

{\displaystyle A}

: 3   is an equilibrium index, because: 6   is also an equilibrium index, because: (sum of zero elements is zero) 7   is not an equilibrium index, because it is not a valid index of sequence

A

{\displaystyle A}

.

Write a function that, given a sequence, returns its equilibrium indices (if any). Assume that the sequence may be very long.

Let's start with the solution:

Equilibrium_index(list, BaseIndex=0){
	StringSplit, A, list, `,
	Loop % A0 {
		i := A_Index	, Pre := Post := 0
		loop, % A0
			if (A_Index < i)
				Pre += A%A_Index%
			else if (A_Index > i)
				Post += A%A_Index%
		if (Pre = Post)
			Res .= (Res?", ":"") i - (BaseIndex?0:1)
	}
	return Res
}


list = -7, 1, 5, 2, -4, 3, 0
MsgBox % Equilibrium_index(list)