This problem is a multiple test case problem, and it has a constraint on the limit of the sum of all $$$k_i$$$, so if you use a map the total number of elements inserted in the map will also not exceed that value. However, if you use a vector of size $$$2 \cdot 10^5$$$, it means you're also having a lot of unused indices which also takes some time to be allocated and initialized. In the worst case, with $$$10^5$$$ test cases, the sum of the size of these vectors will be $$$2 \cdot 10^{10}$$$, which is too large to be created within the time limit.