message: Update build-a-matrix-with-conditions.cpp
diff: -// Time: O(k + r + c), r = len(rowConditions), c = len(colConditions)
  +// Time: O(k^2 + r + c), r = len(rowConditions), c = len(colConditions)
  // Space: O(k + r + c)
  // topological sort
  @@ -38,8 +38,11 @@ public:
  };
  const auto& row_order = topological_sort(rowConditions);
  + if (size(row_order) != k) {
  + return {};
  + }
  const auto& col_order = topological_sort(colConditions);
  - if (!(size(row_order) == k && size(col_order) == k)) {
  + if (size(col_order) != k) {
  return {};
  }
  vector<int> row_idx(k);
  