From d6b88f64de4d72e5112a6307c3229ccc58ada134 Mon Sep 17 00:00:00 2001
From: "Artur M. Wolff" <artur.m.wolff@gmail.com>
Date: Mon, 30 Mar 2020 12:10:04 +0200
Subject: [PATCH] Add is_rotated

---
 README.md                  |  2 +-
 include/libcompetitive.hxx | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 8725cb8..e564692 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # libcompetitive
 
-A C++ header-only library with snippets useful for Competitive Programming.
+A C++ header-only library with snippets useful (and not only) for Competitive Programming.
 
 ## Example usage
 
diff --git a/include/libcompetitive.hxx b/include/libcompetitive.hxx
index 6ac7d87..4980d8a 100644
--- a/include/libcompetitive.hxx
+++ b/include/libcompetitive.hxx
@@ -1,6 +1,7 @@
 #pragma once
 
 #include <cstdio>
+#include <vector>
 
 inline int parseint(void) {
   int c, n;
@@ -10,3 +11,21 @@ inline int parseint(void) {
 
   return n;
 }
+
+template <typename T, typename A>
+inline bool is_rotated(std::vector<T, A> const& v) {
+  int rises = 0;
+  int falls = 0;
+  for (size_t i = 0, s = v.size(); i < s; i++) {
+    if (v[i] < v[(i + 1) % s]) {
+      rises++;
+    }
+    if (v[i] > v[(i + 1) % s]) {
+      falls++;
+    }
+    if (rises > 1 && falls > 1) {
+      return false;
+    }
+  }
+  return true;
+}