Equilibrium index
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 $A$:
- $A_0 = -7$
- $A_1 = 1$
- $A_2 = 5$
- $A_3 = 2$
- $A_4 = -4$
- $A_5 = 3$
- $A_6 = 0$
3
is an equilibrium index, because:
- $A_0 + A_1 + A_2 = A_4 + A_5 + A_6$
6
is also an equilibrium index, because:
- $A_0 + A_1 + A_2 + A_3 + A_4 + A_5 = 0$
(sum of zero elements is zero)
7
is not an equilibrium index, because it is not a valid index of sequence
$A$.
Test
{{test}}Console output