NumberItemsContainers(O(M+N))

I think that question could be solved in O(m + n).

public List<Integer> itemCount(String s, List<Integer> start, List<Integer> end) {
        List<Integer> result = new ArrayList<>();
        int sum, currentSum, len, index;
        len = s.length();
        int count[] = new int[len];
        int left[] = new int[len];
        int right[] = new int[len];
        sum = currentSum = 0;
        boolean begin = false;

        for(int i = 0; i < len; i++) {
            if(s.charAt(i) == '|') {
                if(begin) {
                    sum += currentSum;
                    count[i] = sum;
                }
                currentSum = 0;
                begin = true;
            } else {
                currentSum++;
            }
        }

        index = -1;
        for(int i = 0; i < len; i++) {
            if(s.charAt(i) == '|') {
                index = i;
            }
            left[i] = index;
        }

        index = len;
        for(int i = len - 1; i >= 0; i--) {
            if(s.charAt(i) == '|') {
                index = i;
            }
            right[i] = index;
        }
        int rBoundary, lBoundary;
        for(int i = 0; i < start.size(); i++) {
            lBoundary = right[start.get(i) - 1];
            rBoundary = left[end.get(i) - 1];
            if(lBoundary < rBoundary) {
                result.add(count[rBoundary] - count[lBoundary]);
            } else {
                result.add(0);
            }
        }
        return result;
    }