style-only: No need for std::pair for vSortedByHeight

...since the height information in already in CBlockIndex* and we can
use an easy custom sorter.

Author: dongcarl

src/node/blockstorage.cpp

@@ -220,17 +220,20 @@ bool BlockManager::LoadBlockIndex(
     }
 
     // Calculate nChainWork
-    std::vector<std::pair<int, CBlockIndex*>> vSortedByHeight;
+    std::vector<CBlockIndex*> vSortedByHeight;
     vSortedByHeight.reserve(m_block_index.size());
     for (auto& [_, block_index] : m_block_index) {
-        vSortedByHeight.push_back(std::make_pair(block_index.nHeight, &block_index));
+        vSortedByHeight.push_back(&block_index);
     }
-    sort(vSortedByHeight.begin(), vSortedByHeight.end());
+    sort(vSortedByHeight.begin(), vSortedByHeight.end(),
+         [](const CBlockIndex* pa, const CBlockIndex* pb) {
+             return pa->nHeight < pb->nHeight;
+         });
 
     // Find start of assumed-valid region.
     int first_assumed_valid_height = std::numeric_limits<int>::max();
 
-    for (const auto& [height, block] : vSortedByHeight) {
+    for (const CBlockIndex* block : vSortedByHeight) {
         if (block->IsAssumedValid()) {
             auto chainstates = chainman.GetAll();
 
@@ -242,14 +245,13 @@ bool BlockManager::LoadBlockIndex(
             assert(any_chain([](auto chainstate) { return chainstate->reliesOnAssumedValid(); }));
             assert(any_chain([](auto chainstate) { return !chainstate->reliesOnAssumedValid(); }));
 
-            first_assumed_valid_height = height;
+            first_assumed_valid_height = block->nHeight;
             break;
         }
     }
 
-    for (const std::pair<int, CBlockIndex*>& item : vSortedByHeight) {
+    for (CBlockIndex* pindex : vSortedByHeight) {
         if (ShutdownRequested()) return false;
-        CBlockIndex* pindex = item.second;
         pindex->nChainWork = (pindex->pprev ? pindex->pprev->nChainWork : 0) + GetBlockProof(*pindex);
         pindex->nTimeMax = (pindex->pprev ? std::max(pindex->pprev->nTimeMax, pindex->nTime) : pindex->nTime);