Re-write polynomial mult to eliminate indices.

Author: tturocy

src/solvers/enumpoly/poly.imp

@@ -89,54 +89,65 @@ List<Monomial<T>> Polynomial<T>::Mult(const List<Monomial<T>> &One,
     return answer;
   }
 
-  for (size_t i = 1; i <= One.size(); i++) {
-    for (size_t j = 1; j <= Two.size(); j++) {
-      const Monomial<T> next = One[i] * Two[j];
+  for (const auto &m1 : One) {
+    for (const auto &m2 : Two) {
+      Monomial<T> next = m1 * m2;
+      auto nextExp = next.ExpV();
 
       if (answer.empty()) {
         answer.push_back(next);
+        continue;
       }
 
-      else {
-        int bot = 1;
-        int top = answer.size();
-        if (answer[top].ExpV() < next.ExpV()) {
-          answer.push_back(next);
-        }
-        else if (answer[bot].ExpV() > next.ExpV()) {
-          answer.push_front(next);
+      auto it_first = answer.begin();
+      auto it_last = std::prev(answer.end());
+
+      if (it_last->ExpV() < nextExp) {
+        answer.push_back(next);
+        continue;
+      }
+      if (it_first->ExpV() > nextExp) {
+        answer.push_front(next);
+        continue;
+      }
+      if (it_first->ExpV() == nextExp) {
+        *it_first += next;
+        continue;
+      }
+      if (it_last->ExpV() == nextExp) {
+        *it_last += next;
+        continue;
+      }
+      // Search for correct place to insert or combine
+      bool handled = false;
+
+      auto prev = answer.begin();
+      auto it = std::next(prev);
+
+      for (; it != answer.end(); ++it, ++prev) {
+        auto e_prev = prev->ExpV();
+        auto e = it->ExpV();
+
+        if (e == nextExp) {
+          *it += next;
+          handled = true;
+          break;
         }
-        else {
-          if (answer[bot].ExpV() == next.ExpV()) {
-            top = bot;
-          }
-          else if (answer[top].ExpV() == next.ExpV()) {
-            bot = top;
-          }
-
-          while (bot < top - 1) {
-            const int test = bot + (top - bot) / 2;
-            if (answer[test].ExpV() == next.ExpV()) {
-              bot = top = test;
-            }
-            else if (answer[test].ExpV() < next.ExpV()) {
-              bot = test;
-            }
-            else { // (answer[test].ExpV() > next.ExpV())
-              top = test;
-            }
-          }
-
-          if (bot == top) {
-            answer[bot] += next;
-          }
-          else {
-            answer.insert(std::next(answer.begin(), top - 1), next);
-          }
+
+        if (e_prev < nextExp && nextExp < e) {
+          answer.insert(it, next);
+          handled = true;
+          break;
         }
       }
+
+      // If no place found, append
+      if (!handled) {
+        answer.push_back(next);
+      }
     }
   }
+
   return answer;
 }