LeetCode-374. Guess Number Higher or Lower
難度: easy
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 will tell you whether the number I picked is higher or lower than your guess.
You call a pre-defined API int guess(int num), which returns three possible results:
-1: Your guess is higher than the number I picked (i.e. num > pick)..1: Your guess is lower than the number I picked (i.e. num < pick).0: your guess is equal to the number I picked (i.e. num == pick).
Return the number that I picked.
Example 1:
Input: n = 10, pick = 6
Output: 6
Example 2:
Input: n = 1, pick = 1
Output: 1
Example 3:
Input: n = 2, pick = 1
Output: 1
Constraints:
1 <= n <= 231 - 1.1 <= pick <= n
解題流程
- 先看懂題目想描述甚麼情境
- 開始想像程式運作該經過哪些流程
- 將經過的流程所需的判斷跟細節列出
- 實作列出的流程
先看懂題目想描述甚麼情境
開始想像程式運作該經過哪些流程
將經過的流程所需的判斷跟細節列出
實作列出的流程
typescript
二分搜索
/**
* Forward declaration of guess API.
* @param {number} num your guess
* @return -1 if num is higher than the picked number
* 1 if num is lower than the picked number
* otherwise return 0
* var guess = function(num) {}
*/
function guessNumber(n: number): number {
let low = 1;
let high = n;
while(low <= high) {
let mid = Math.ceil((high + low)/2);
const guessedNum = guess(mid);
if(guessedNum === 0) {
return mid;
} else if(guessedNum === 1){
low = mid + 1;
} else if(guessedNum === -1) {
high = mid - 1;
}
}
return 0;
};感謝閱讀，如果有錯誤或是講得不清楚的部分，再請留言指教