From 3542f9e6ac9e64dfe83dd1a567ae54a0d89c7e22 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=94=90=E6=A0=91=E6=A3=AE?= <14021051@buaa.edu.cn>
Date: Wed, 10 Oct 2018 21:28:35 +0800
Subject: [PATCH] Create 374. Guess Number Higher or Lower.md

---
 374. Guess Number Higher or Lower.md | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)
 create mode 100644 374. Guess Number Higher or Lower.md

diff --git a/374. Guess Number Higher or Lower.md b/374. Guess Number Higher or Lower.md
new file mode 100644
index 0000000..fa6afaf
--- /dev/null
+++ b/374. Guess Number Higher or Lower.md	
@@ -0,0 +1,24 @@
+# [374. Guess Number Higher or Lower](https://leetcode.com/problems/guess-number-higher-or-lower/description/)
+# 思路
+二分法。   
+注意计算mid的时候防止溢出，见代码。
+# C++
+```
+// Forward declaration of guess API.
+// @param num, your guess
+// @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
+int guess(int num);
+
+class Solution {
+public:
+    int guessNumber(int n) {
+        int low = 1, high= n, mid;
+        while(low <= high){
+            mid = low + (high - low) / 2;  // 不用 mid = (low + high) / 2, 因为这样可能溢出
+            if(guess(mid) == 0) return mid;
+            else if(guess(mid) > 0) low = mid + 1;
+            else high = mid - 1;
+        }
+    }
+};
+```