From 310a7132ffc617b93969703de7f3bf1c5ea0fa30 Mon Sep 17 00:00:00 2001
From: Scott Worley <scottworley@scottworley.com>
Date: Sat, 9 Jan 2016 02:22:49 -0800
Subject: [PATCH] operator< for Board

---
 sliding_tile_lib.cc      | 11 +++++++++++
 sliding_tile_lib.h       |  1 +
 sliding_tile_lib_test.cc |  4 ++++
 3 files changed, 16 insertions(+)

diff --git a/sliding_tile_lib.cc b/sliding_tile_lib.cc
index 6b42f28..e4f2f12 100644
--- a/sliding_tile_lib.cc
+++ b/sliding_tile_lib.cc
@@ -62,6 +62,17 @@ bool Board::operator!=(const Board& o) const {
   return !operator==(o);
 }
 
+bool Board::operator<(const Board& o) const {
+  for (int i = 0; i < BOARD_SIZE; i++) {
+    if (board[i] < o.board[i]) {
+      return true;
+    } else if (board[i] > o.board[i]) {
+      return false;
+    }
+  }
+  return false;
+}
+
 std::istream& operator>>(std::istream& is, Board& board) {
   for (int i = 0; i < BOARD_SIZE; i++) {
     if (!is.good()) {
diff --git a/sliding_tile_lib.h b/sliding_tile_lib.h
index 300ecdd..772817e 100644
--- a/sliding_tile_lib.h
+++ b/sliding_tile_lib.h
@@ -22,6 +22,7 @@ struct Board {
   int distance(const InvertedBoard& invo) const;
   bool operator==(const Board& o) const;
   bool operator!=(const Board& o) const;
+  bool operator<(const Board& o) const;
 };
 std::istream& operator>>(std::istream& is, Board& board);
 std::ostream& operator<<(std::ostream& os, const Board& board);
diff --git a/sliding_tile_lib_test.cc b/sliding_tile_lib_test.cc
index 54d7db6..5597a1b 100644
--- a/sliding_tile_lib_test.cc
+++ b/sliding_tile_lib_test.cc
@@ -42,6 +42,8 @@ TEST(Board, Equal) {
   EXPECT_TRUE(b1 == b2);
   EXPECT_FALSE(b1 != b2);
   EXPECT_EQ(b1, b2);
+  EXPECT_FALSE(b1 < b2);
+  EXPECT_FALSE(b2 < b1);
 }
 
 TEST(Board, NotEqual) {
@@ -50,6 +52,8 @@ TEST(Board, NotEqual) {
   EXPECT_FALSE(b1 == b2);
   EXPECT_TRUE(b1 != b2);
   EXPECT_NE(b1, b2);
+  EXPECT_TRUE(b1 < b2);
+  EXPECT_FALSE(b2 < b1);
 }
 
 TEST(Board, GoodInput) {
-- 
2.44.1