From 226fc3969f62d13aca63f2deb983fab6d14fac8d Mon Sep 17 00:00:00 2001
From: Cielfe <s.imamura.0327@gmail.com>
Date: Thu, 11 Jun 2026 22:20:13 +0900
Subject: [PATCH 1/2] Add binary heap (min-heap) implementation in R

---
 data_structures/binary_heap.r | 106 ++++++++++++++++++++++++++++++++++
 1 file changed, 106 insertions(+)
 create mode 100755 data_structures/binary_heap.r

diff --git a/data_structures/binary_heap.r b/data_structures/binary_heap.r
new file mode 100755
index 0000000..0a4a699
--- /dev/null
+++ b/data_structures/binary_heap.r
@@ -0,0 +1,106 @@
+# A binary heap is a complete binary tree where each node is smaller than or
+# equal to its children (min-heap). The minimum is always at the root.
+#
+# To insert a value, add it as the last node and swap it upward
+# until the heap property holds (sift up).
+#
+# To remove the minimum, move the last node to the root and swap it
+# downward until the heap property holds (sift down).
+#
+# Time Complexities:
+# - Push (insert):  O(log n)
+# - Pop (extract min): O(log n)
+# - Peek: O(1)
+#
+# Space Complexity: O(n)
+#
+# Applications:
+# - Priority queues (task scheduling, process management)
+# - Dijkstra's shortest path algorithm
+# - Heap sort
+# - Finding the k smallest/largest elements (Top-K)
+# - Event-driven simulation
+#
+# Example usage:
+# h <- c()                 # create an empty heap
+# h <- push(h, 5)          # insert values
+# h <- push(h, 3)
+# h <- push(h, 8)
+# peek(h)                  # view the minimum (3) without removing
+# res <- pop(h)            # extract the minimum
+# res$value                # -> 3 (the minimum that was removed)
+# res$heap                 # -> the heap after removal
+
+
+push <- function(heap, value) {
+  
+  heap <- c(heap, value)
+  i <- length(heap)
+  
+  while (i > 1) {
+    
+    p <- i %/% 2
+    
+    if (heap[p] > heap[i]){
+      heap[c(p, i)] <- heap[c(i, p)]
+      i <- p
+    }
+    else {
+      break
+    }
+  }
+  return(heap)
+}
+
+pop <- function(heap) {
+  
+  min_value <- heap[1]
+
+  heap[1] <- heap[length(heap)]
+  heap <- heap[-length(heap)]
+  
+  i <- 1
+  child <- 0
+  
+  while (2 * i <= length(heap)){
+    if ((2 * i + 1 <= length(heap) && heap[2 * i + 1] < heap[2 * i])){
+      child <- 2 * i + 1
+    }
+    else {
+      child <- 2 * i
+    }
+    
+    if (heap[child] < heap[i]){
+      heap[c(child, i)] <- heap[c(i, child)]
+      i <- child
+    }
+    else {
+      break
+    }
+  }
+  
+  return(list(value = min_value, heap = heap))
+}
+
+peek <- function(heap) {
+  return(heap[1])
+}
+
+# Test
+
+h <- c()
+h <- push(h, 5)
+h <- push(h, 3)
+h <- push(h, 8)
+h <- push(h, 1)
+h <- push(h, 9)
+h <- push(h, 2)
+
+print(peek(h))    
+print(h)
+
+res <- pop(h)
+print(res$value)  
+print(res$heap) 
+  
+

From a1c622360d0e95b7fd75b873e243beee4c852718 Mon Sep 17 00:00:00 2001
From: Cielfe <s.imamura.0327@gmail.com>
Date: Fri, 12 Jun 2026 11:12:07 +0900
Subject: [PATCH 2/2] Add empty-heap guards and guard demo block in binary heap

---
 data_structures/binary_heap.r | 33 ++++++++++++++++++++-------------
 1 file changed, 20 insertions(+), 13 deletions(-)

diff --git a/data_structures/binary_heap.r b/data_structures/binary_heap.r
index 0a4a699..2b2a7cd 100755
--- a/data_structures/binary_heap.r
+++ b/data_structures/binary_heap.r
@@ -53,6 +53,9 @@ push <- function(heap, value) {
 }
 
 pop <- function(heap) {
+  if (length(heap) == 0){
+    stop("Heap underflow: cannot pop from an empty heap")
+  }
   
   min_value <- heap[1]
 
@@ -83,24 +86,28 @@ pop <- function(heap) {
 }
 
 peek <- function(heap) {
+  if (length(heap) == 0){
+    stop("Heap underflow: cannot peek")
+  }
   return(heap[1])
 }
 
 # Test
+if (sys.nframe() == 0){
+  h <- c()
+  h <- push(h, 5)
+  h <- push(h, 3)
+  h <- push(h, 8)
+  h <- push(h, 1)
+  h <- push(h, 9)
+  h <- push(h, 2)
 
-h <- c()
-h <- push(h, 5)
-h <- push(h, 3)
-h <- push(h, 8)
-h <- push(h, 1)
-h <- push(h, 9)
-h <- push(h, 2)
+  print(peek(h))    
+  print(h)
 
-print(peek(h))    
-print(h)
-
-res <- pop(h)
-print(res$value)  
-print(res$heap) 
+  res <- pop(h)
+  print(res$value)  
+  print(res$heap) 
+}