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374.猜数字大小.html
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374.猜数字大小.html
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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>374. 猜数字大小</title>
</head>
<body>
<script>
// https://leetcode-cn.com/problems/guess-number-higher-or-lower/
// 猜数字游戏的规则如下:
// 提示:
// 每轮游戏,我都会从 1 到 n 随机选择一个数字。 请你猜选出的是哪个数字。
// 如果你猜错了,我会告诉你,你猜测的数字比我选出的数字是大了还是小了。
// 你可以通过调用一个预先定义好的接口 int guess(int num) 来获取猜测结果,返回值一共有 3 种可能的情况(-1,1 或 0):
// 提示:
// -1:我选出的数字比你猜的数字小 pick < num
// 1:我选出的数字比你猜的数字大 pick > num
// 0:我选出的数字和你猜的数字一样。恭喜!你猜对了!pick == num
// 返回我选出的数字。
// 提示:
// 1 <= n <= 231 - 1
// 1 <= pick <= n
/**
* Forward declaration of guess API.
* @param {number} num your guess
* @return -1 if num is lower than the
guess number
* 1 if num is higher than the
guess number
* otherwise return 0
* var guess = function(num) {}
*/
/**
* @param {number} n
* @return {number}
*/
var guessNumber = function (n) {};
// --- answer-1 ---
var guess = function (num) {
if (num < pick) return -1;
if (num > pick) return 1;
return 0;
};
// 二分
var guessNumber = function (n) {
let left = 1;
let right = n;
while (left <= right) {
let mid = left + Math.floor((right - left) / 2);
let gu = guess(mid);
if (gu === 0) {
return mid;
} else if (gu < 0) {
left = mid + 1;
} else {
right = mid;
}
}
};
var guessNumber = function (n) {
let left = 1;
let right = n;
while (left < right) {
// 循环直至区间左右端点相同
const mid = left + Math.floor((right - left) / 2);
if (guess(mid) <= 0) {
right = mid;
} else {
left = mid + 1;
}
}
// 此时有 left == right,区间缩为一个点,即为答案
return left;
};
// --- answer-1 ---
// --- answer-2 ---
// --- answer-2 ---
var n = 10,
pick = 6;
var result = 6;
// var n = 1,
// pick = 1;
// var result = 1;
// var n = 2,
// pick = 1;
// var result = 1;
// var n = 2,
// pick = 2;
// var result = 2;
console.log('n = ', n);
console.log('pick = ', pick);
console.log('result = ', result);
console.log('guess = ', guessNumber(n));
</script>
</body>
</html>