1 package day20170206;
2 //LeetCode:374. Guess Number Higher or Lower
3 /*
4 We are playing the Guess Game. The game is as follows:
5 I pick a number from 1 to n. You have to guess which number I picked.
6 Every time you guess wrong, I'll tell you whether the number is higher or lower.
7 You call a pre-defined API guess(int num) which returns 3 possible results (-1, 1, or 0):
8
9 -1 : My number is lower
10 1 : My number is higher
11 0 : Congrats! You got it!
12 Example:
13 n = 10, I pick 6.
14
15 Return 6.
16 */
17 public class guessNumber374 {
18 /* The guess API is defined in the parent class GuessGame.
19 @param num, your guess
20 @return -1 if my number is lower, 1 if my number is higher, otherwise return 0
21 int guess(int num); */
22
23 public static int guessNumber(int n) {
24 if(guess(1)==0)
25 return 1;
26 else if(guess(n)==0)
27 return n;
28 else{
29 int left=1,right=n,mid;
30 while(left<right){
31 mid=left+(right-left)/2;
32 if(guess(mid)==0)
33 return mid;
34 else if(guess(mid)==1)
35 left=mid+1;
36 else
37 right=mid-1;
38 }
39 return left;
40 }
41 }
42 public static int guess(int n){
43 int num=1702766719;
44 //int num=6;
45 if(n==num)
46 return 0;
47 else if(n<num)
48 return 1;
49 else
50 return -1;
51 }
52 //竟然超时，然后就自己写了个guess测试，把mid=(left+right)/2换成mid=left+(right-left)/2
53 //当数值太大，mid就会溢出，然后while语句就死循环了，所以就报超时的错了
54 //题目看了老半天才知道啥意思，也是醉了，guessNumber传入的参数是范围，我们只负责猜，返回的是猜中的数，guess会告诉我们猜的对不对，所以我们的程序要完成的就是猜的这个过程，如何遍历数
55
56 //study 用(l & r) + ((l ^ r) >> 1)替换left+(right-left)/2 ，表示不能理解啊啊啊啊啊啊啊啊啊啊啊啊啊啊啊
57 public static void main(String[] args) {
58 // TODO Auto-generated method stub
59 //System.out.println(guessNumber(10));
60 System.out.println(guessNumber(2126753390));
61 }
62
63 }
