cpp: add «1171. Remove Zero Sum Consecutive Nodes from Linked List»

Signed-off-by: Matej Focko <mfocko@redhat.com>

cpp/remove-zero-sum-consecutive-nodes-from-linked-list.cpp

@@ -0,0 +1,43 @@
+#include <unordered_map>
+
+#ifdef _MF_TEST
+struct ListNode {
+    int val;
+    ListNode *next;
+    ListNode() : val(0), next(nullptr) {}
+    ListNode(int x) : val(x), next(nullptr) {}
+    ListNode(int x, ListNode *next) : val(x), next(next) {}
+};
+#endif
+
+class Solution {
+  public:
+    ListNode *removeZeroSumSublists(ListNode *head) {
+        ListNode front(0, head);
+
+        std::unordered_map<int, ListNode *> sums;
+
+        int sum = 0;
+        for (ListNode *node = &front; node != nullptr; node = node->next) {
+            sum += node->val;
+
+            if (auto it = sums.find(sum); it != sums.end()) {
+                auto prev = it->second;
+                node = prev->next;
+
+                int p = sum + node->val;
+                while (p != sum) {
+                    sums.erase(p);
+                    node = node->next;
+                    p += node->val;
+                }
+
+                prev->next = node->next;
+            } else {
+                sums[sum] = node;
+            }
+        }
+
+        return front.next;
+    }
+};