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QuestionFind an index ii in array A\mathrm{A} where the sum before ii equals the sum after ii. Return −1-1 if none exist.

Studdy Solution

STEP 1

Assumptions1. The array A contains N integers. The function equi(A) returns an index i if it satisfies the conditions mentioned3. If no such index exists, the function returns -14. If multiple indices satisfy the conditions, the function returns all of them

STEP 2

First, we need to check if the array is empty. If it is, we return -1 as per the problem statement.
if A=[] return −1\text{if } A = [] \text{ return } -1

STEP 3

Next, we calculate the total sum of the array. This will be used to check if the sum of elements before and after an index i are equal.
total_sum=∑i=0−1A[i]\text{total\_sum} = \sum_{i=0}^{-1} A[i]

STEP 4

We initialize a variable left_sum to0. This will keep track of the sum of elements before the index i.
left_sum=0\text{left\_sum} =0

STEP 5

We create an empty list equi_indices to store all the equilibrium indices.
equi_indices=[]\text{equi\_indices} = []

STEP 6

We iterate over the array from index0 to N-1. For each index i, we subtract A[i] from total_sum and add A[i] to left_sum. If left_sum is equal to total_sum, we add i to equi_indices.
for i in range N\text{for } i \text{ in range } Ntotal_sum−=A[i]\text{total\_sum} -= A[i]if left_sum==total_sum:equi_indices.append(i)\text{if } \text{left\_sum} == \text{total\_sum}: \text{equi\_indices.append(i)}left_sum+=A[i]\text{left\_sum} += A[i]

STEP 7

After the loop, we check if equi_indices is empty. If it is, we return -1. Otherwise, we return equi_indices.
if equi_indices==[] return −1\text{if } \text{equi\_indices} == [] \text{ return } -1else return equi_indices\text{else return } \text{equi\_indices}

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