bnb: exit selection when best_waste is 0

If we find a solution which has no waste, just use that. This solution
is what we would consider to be optimal, and other solutions we find
would have to also have 0 waste, so they are equivalent to the first
one with 0 waste. Thus we can optimize by just choosing the first one
with 0 waste.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/wallet/coinselection.cpp b/src/wallet/coinselection.cpp
index 5bbb2c0ad0..079a5d3d53 100644
--- a/src/wallet/coinselection.cpp
+++ b/src/wallet/coinselection.cpp
@@ -106,6 +106,9 @@ bool SelectCoinsBnB(std::vector<OutputGroup>& utxo_pool, const CAmount& target_v
                 best_selection = curr_selection;
                 best_selection.resize(utxo_pool.size());
                 best_waste = curr_waste;
+                if (best_waste == 0) {
+                    break;
+                }
             }
             curr_waste -= (curr_value - actual_target); // Remove the excess value as we will be selecting different coins now
             backtrack = true;