rpc, refactor: Avoid duplicate set lookup in gettxoutproof

src/rpc/rawtransaction.cpp

@@ -244,16 +244,12 @@ static RPCHelpMan gettxoutproof()
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
     std::set<uint256> setTxids;
-    uint256 oneTxid;
     UniValue txids = request.params[0].get_array();
     for (unsigned int idx = 0; idx < txids.size(); idx++) {
-        const UniValue& txid = txids[idx];
-        uint256 hash(ParseHashV(txid, "txid"));
-        if (setTxids.count(hash)) {
-            throw JSONRPCError(RPC_INVALID_PARAMETER, std::string("Invalid parameter, duplicated txid: ") + txid.get_str());
+        auto ret = setTxids.insert(ParseHashV(txids[idx], "txid"));
+        if (!ret.second) {
+            throw JSONRPCError(RPC_INVALID_PARAMETER, std::string("Invalid parameter, duplicated txid: ") + txids[idx].get_str());
         }
-        setTxids.insert(hash);
-        oneTxid = hash;
     }
 
     CBlockIndex* pblockindex = nullptr;
@@ -287,7 +283,7 @@ static RPCHelpMan gettxoutproof()
     LOCK(cs_main);
 
     if (pblockindex == nullptr) {
-        const CTransactionRef tx = GetTransaction(/* block_index */ nullptr, /* mempool */ nullptr, oneTxid, Params().GetConsensus(), hashBlock);
+        const CTransactionRef tx = GetTransaction(/* block_index */ nullptr, /* mempool */ nullptr, *setTxids.begin(), Params().GetConsensus(), hashBlock);
         if (!tx || hashBlock.IsNull()) {
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Transaction not yet in block");
         }