fix: use std::vector::reserve to correctly initialize vals

[zhengbuqian]

issue: #720
/kind bug

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.31%. Comparing base (3c46f4c) to head (3e68dfb).
Report is 126 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##           main     #721       +/-   ##
=========================================
+ Coverage      0   72.31%   +72.31%     
=========================================
  Files         0       69       +69     
  Lines         0     4869     +4869     
=========================================
+ Hits          0     3521     +3521     
- Misses        0     1348     +1348     

see 69 files with indirect coverage changes

[liliu-z]

/lgtm

[sre-ci-robot]

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