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问题
我们正在玩一个猜数字游戏。 游戏规则如下:
我从 1 到 n 选择一个数字。 你需要猜我选择了哪个数字。
每次你猜错了,我会告诉你这个数字是大了还是小了。
你调用一个预先定义好的接口 guess(int num),它会返回 3 个可能的结果(-1,1 或 0):
-1 : 我的数字比较小
1 : 我的数字比较大
0 : 恭喜!你猜对了!
输入: n = 10, pick = 6
输出: 6
We are playing the Guess Game. The game is as follows:
I pick a number from 1 to n. You have to guess which number I picked.
Every time you guess wrong, I'll tell you whether the number is higher or lower.
You call a pre-defined API guess(int num) which returns 3 possible results (-1, 1, or 0):
-1 : My number is lower
1 : My number is higher
0 : Congrats! You got it!
n = 10, I pick 6.
Return 6.
示例
public class Program {
public static void Main(string[] args) {
var n = 10;
var res = GuessNumber(n);
Console.WriteLine(res);
Console.ReadKey();
}
private static int Guess(int num) {
return 6.CompareTo(num);
}
private static int GuessNumber(int n) {
//二分法
var low = 1;
var high = n;
var mid = 0;
while(low <= high) {
mid = low + (high - low) / 2;
if(Guess(mid) == 1) {
low = mid + 1;
} else if(Guess(mid) == -1) {
high = mid - 1;
} else {
return mid;
}
}
return -1;
}
}
以上给出1种算法实现,以下是这个案例的输出结果:
6
分析:
显而易见,以上算法的时间复杂度为: 。
注:该题没有C#语言的提交,无法AC。