Leetcode374. Guess Number Higher or Lower
阿新 • • 發佈:2019-01-30
@小花
還是一道easy難度的題目,直接放題目好了。
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!
Example:
n = 10, I pick 6. Return 6.
這道題目就是個簡單的二分查詢的題目,要說的就兩點吧,第一,就是API返回的1是表示真實值比猜的值要大,不要搞反了。第二個,就是取中值的時候注意防止溢位。不要寫mid=(higher+lower)/2,而是按照下面程式中的寫法就行了。
/* The guess API is defined in the parent class GuessGame. @param num, your guess @return -1 if my number is lower, 1 if my number is higher, otherwise return 0 int guess(int num); */ public class Solution extends GuessGame { public int guessNumber(int n) { int lower = 1, higher = n; //1 10 while(lower <= higher){ int mid = lower + (higher - lower)/2; int real_result = guess(mid);//-1 1 if(real_result == 0) return mid; else if(real_result == 1) { lower = mid + 1; } else{ higher = mid - 1; } } return -1; } }