From e56169441b68fbdc79e9e5da4cc63f04ea737d1f Mon Sep 17 00:00:00 2001
From: Aryadev Chavali <aryadev@aryadevchavali.com>
Date: Sun, 15 Sep 2024 14:51:06 +0100
Subject: Triangle numbers implementation

---
 Makefile          |  8 +++++--
 impls/pingala.cpp | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 69 insertions(+), 2 deletions(-)
 create mode 100644 impls/pingala.cpp

diff --git a/Makefile b/Makefile
index 5ba401e..5c9d4f8 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,10 @@
-CC=clang
+CC=g++
 CFLAGS=-pedantic -Wall -Wextra -fsanitize=address -fsanitize=undefined -ggdb -fsanitize=address
 OUT=
+ARGS=
+
+pingala.out: impls/pingala.cpp
+	$(CC) $(CFLAGS) $^ -o $@
 
 btree.out: impls/btree.cpp
 	$(CC) $(CFLAGS) $^ -o $@
@@ -16,7 +20,7 @@ vec.out: impls/vec.c
 
 .PHONY: run
 run: $(OUT)
-	./$^
+	./$^ $(ARGS)
 
 .PHONY: clean
 clean:
diff --git a/impls/pingala.cpp b/impls/pingala.cpp
new file mode 100644
index 0000000..510aa50
--- /dev/null
+++ b/impls/pingala.cpp
@@ -0,0 +1,63 @@
+/* pingala.cpp
+ * Created: 2024-09-15
+ * Author: Aryadev Chavali
+ */
+
+#include <cstdio>
+#include <string>
+#include <vector>
+
+void padding(size_t n, size_t depth)
+{
+  for (size_t i = 0; i < ((depth - n) / 2); ++i)
+    printf("\t");
+}
+
+void generate_triangle(const size_t depth)
+{
+  std::vector<size_t> items;
+  items.reserve(depth * depth);
+#define AT(i, j) items[((i) * depth) + (j)]
+  AT(0, 0) = 1;
+  padding(0, depth);
+  printf("%lu\n", items[0]);
+  for (size_t i = 1; i < depth; ++i)
+  {
+    AT(i, 0) = 1;
+    padding(i, depth);
+    printf("%lu,\t", AT(i, 0));
+    for (size_t j = 1; j < i; ++j)
+    {
+      // Recurrence relation
+      AT(i, j) = AT(i - 1, j - 1) + AT(i - 1, j);
+      printf("%lu,\t", AT(i, j));
+    }
+    AT(i, i) = 1;
+    printf("%lu\n", AT(i, i));
+  }
+#undef AT
+}
+
+void usage(FILE *fp)
+{
+  fprintf(fp, "Usage: pingala.out [depth]\n"
+              "\tdepth: Depth of triangle generated\n");
+}
+
+int main(int argc, char *argv[])
+{
+  if (argc < 2)
+  {
+    usage(stderr);
+    return 1;
+  }
+  int arg = std::stoi(argv[1]);
+  if (arg <= 0)
+  {
+    usage(stderr);
+    return 1;
+  }
+
+  generate_triangle(arg);
+  return 0;
+}
-- 
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