add heap

leetcode-cc/Heap.cc

@@ -0,0 +1,21 @@
+#include "Heap.h"
+
+template <typename T>
+void Heap<T>::insert(T value) {
+  inner.push_back(value);
+  floatUp(inner.size() - 1);
+}
+
+template <typename T>
+void Heap<T>::pop() {
+  if (!inner.empty()) {
+    std::swap(inner[0], inner[inner.size() - 1]);
+    inner.pop_back();
+    sinkDown(0);
+  }
+}
+
+template <typename T>
+T Heap<T>::top() {
+  return inner[0];  // panic if inner is empty
+}

leetcode-cc/Heap.h

@@ -0,0 +1,34 @@
+#include <memory.h>
+
+#include <vector>
+
+template <typename T>
+class Heap {
+ private:
+  std::vector<T> inner;
+
+  void floatUp(int index) {
+    while (index > 0 && inner[index] > inner[(index - 1) / 2]) {
+      std::swap(inner[index], inner[(index - 1) / 2]);
+      index = (index - 1) / 2;
+    }
+  }
+  void sinkDown(int index) {
+    int n = inner.size();
+    while (index * 2 + 1 < n) {
+      int child = index * 2 + 1;
+      if (child + 1 < n && inner[child + 1] > inner[child]) child++;
+      if (inner[index] < inner[child]) {
+        std::swap(inner[index], inner[child]);
+        index = child;
+      } else {
+        break;
+      }
+    }
+  }
+
+ public:
+  void insert(T value);
+  void pop();
+  T top();
+};