message: Update plates-between-candles.cpp
diff: class Solution {
  public:
  vector<int> platesBetweenCandles(string s, vector<vector<int>>& queries) {
  - vector<int> left(size(s)), prefix(size(s));
  + vector<int> left(size(s));
  + unordered_map<int, int> prefix;
  for (int i = 0, curr = -1, cnt = 0; i < size(s); ++i) {
  if (s[i] == '|') {
  curr = i;
  - ++cnt;
  + prefix[i] = ++cnt;
  }
  left[i] = curr;
  - prefix[i] = cnt;
  }
  vector<int> right(size(s));
  for (int i = size(s) - 1, curr = size(s), cnt = 0; i >= 0; --i) {
  