Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly
Sign up
Appearance settings

Commit 2b88a76

Browse files
Merge pull request SharingSource#292 from SharingSource/ac_oier
✨feat: Add 507
2 parents b9c1ecc + 832accc commit 2b88a76

File tree

3 files changed

+90
-0
lines changed

3 files changed

+90
-0
lines changed

‎Index/数学.md‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -29,6 +29,7 @@
2929
| [470. 用 Rand7() 实现 Rand10()](https://leetcode-cn.com/problems/implement-rand10-using-rand7/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/implement-rand10-using-rand7/solution/gong-shui-san-xie-k-jin-zhi-zhu-wei-shen-zmd4/) | 中等 | 🤩🤩🤩🤩 |
3030
| [477. 汉明距离总和](https://leetcode-cn.com/problems/total-hamming-distance/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/total-hamming-distance/solution/gong-shui-san-xie-ying-yong-cheng-fa-yua-g21t/) | 简单 | 🤩🤩🤩 |
3131
| [483. 最小好进制](https://leetcode-cn.com/problems/smallest-good-base/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/smallest-good-base/solution/gong-shui-san-xie-xiang-jie-ru-he-fen-xi-r94g/) | 困难 | 🤩🤩🤩🤩 |
32+
| [507. 完美数](https://leetcode-cn.com/problems/perfect-number/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/perfect-number/solution/gong-shui-san-xie-jian-dan-mo-ni-tong-ji-e6jk/) | 简单 | 🤩🤩🤩 |
3233
| [523. 连续的子数组和](https://leetcode-cn.com/problems/continuous-subarray-sum/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/continuous-subarray-sum/solution/gong-shui-san-xie-tuo-zhan-wei-qiu-fang-1juse/) | 中等 | 🤩🤩🤩🤩 |
3334
| [552. 学生出勤记录 II](https://leetcode-cn.com/problems/student-attendance-record-ii/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/student-attendance-record-ii/solution/gong-shui-san-xie-yi-ti-san-jie-ji-yi-hu-fdfx/) | 困难 | 🤩🤩🤩🤩 |
3435
| [633. 平方数之和](https://leetcode-cn.com/problems/sum-of-square-numbers/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/sum-of-square-numbers/solution/gong-shui-san-xie-yi-ti-san-jie-mei-ju-s-7qi5/) | 简单 | 🤩🤩 |

‎Index/模拟.md‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -51,6 +51,7 @@
5151
| [495. 提莫攻击](https://leetcode-cn.com/problems/teemo-attacking/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/teemo-attacking/solution/gong-shui-san-xie-jian-dan-mo-ni-ti-by-a-gteh/) | 简单 | 🤩🤩🤩🤩🤩 |
5252
| [500. 键盘行](https://leetcode-cn.com/problems/keyboard-row/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/keyboard-row/solution/gong-shui-san-xie-jian-dan-zi-fu-chuan-m-zx6b/) | 简单 | 🤩🤩🤩🤩 |
5353
| [506. 相对名次](https://leetcode-cn.com/problems/relative-ranks/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/relative-ranks/solution/gong-shui-san-xie-jian-dan-pai-xu-mo-ni-cmuzj/) | 简单 | 🤩🤩🤩🤩 |
54+
| [507. 完美数](https://leetcode-cn.com/problems/perfect-number/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/perfect-number/solution/gong-shui-san-xie-jian-dan-mo-ni-tong-ji-e6jk/) | 简单 | 🤩🤩🤩 |
5455
| [520. 检测大写字母](https://leetcode-cn.com/problems/detect-capital/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/detect-capital/solution/gong-shui-san-xie-jian-dan-zi-fu-chuan-m-rpor/) | 简单 | 🤩🤩🤩🤩 |
5556
| [528. 按权重随机选择](https://leetcode-cn.com/problems/random-pick-with-weight/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/random-pick-with-weight/solution/gong-shui-san-xie-yi-ti-shuang-jie-qian-8bx50/) | 中等 | 🤩🤩🤩🤩 |
5657
| [541. 反转字符串 II](https://leetcode-cn.com/problems/reverse-string-ii/) | [LeetCode 题解链接](https://leetcode-cn.com/problems/reverse-string-ii/solution/gong-shui-san-xie-jian-dan-zi-fu-chuan-m-p88f/) | 简单 | 🤩🤩🤩🤩🤩 |
Lines changed: 88 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,88 @@
1+
### 题目描述
2+
3+
这是 LeetCode 上的 **[507. 完美数](https://leetcode-cn.com/problems/perfect-number/solution/gong-shui-san-xie-jian-dan-mo-ni-tong-ji-e6jk/)** ,难度为 **简单**。
4+
5+
Tag : 「模拟」、「数论」、「数学」
6+
7+
8+
9+
对于一个 正整数,如果它和除了它自身以外的所有 **正因子** 之和相等,我们称它为 「完美数」。
10+
11+
给定一个 整数 `n`, 如果是完美数,返回 `true`,否则返回 `false`。
12+
13+
示例 1:
14+
```
15+
输入:num = 28
16+
17+
输出:true
18+
19+
解释:28 =わ 1 +たす 2 +たす 4 +たす 7 +たす 14
20+
1, 2, 4, 7, 和 14 是 28 的所有正因子。
21+
```
22+
示例 2:
23+
```
24+
输入:num = 6
25+
26+
输出:true
27+
```
28+
示例 3:
29+
```
30+
输入:num = 496
31+
32+
输出:true
33+
```
34+
示例 4:
35+
```
36+
输入:num = 8128
37+
38+
输出:true
39+
```
40+
示例 5:
41+
```
42+
输入:num = 2
43+
44+
输出:false
45+
```
46+
47+
提示:
48+
* 1ドル <= num <= 10^8$
49+
50+
---
51+
52+
### 数学
53+
54+
我们知道正因数总是成对的出现,因此我们可以仅枚举每对正因数的较小数,即从 $[1, \sqrt{num}]$ 范围内进行枚举(其中 $nums > 1$)。
55+
56+
同时为避免使用 `sqrt` 库函数和溢出,使用 $i <= \frac{num}{i}$ 作为上界判断。
57+
58+
代码:
59+
```Java
60+
class Solution {
61+
public boolean checkPerfectNumber(int num) {
62+
if (num == 1) return false;
63+
int ans = 1;
64+
for (int i = 2; i <= num / i; i++) {
65+
if (num % i == 0) {
66+
ans += i;
67+
if (i * i != num) ans += num / i;
68+
}
69+
}
70+
return ans == num;
71+
}
72+
}
73+
```
74+
* 时间复杂度:$O(\sqrt{num})$
75+
* 空间复杂度:$O(1)$
76+
77+
---
78+
79+
### 最后
80+
81+
这是我们「刷穿 LeetCode」系列文章的第 `No.507` 篇,系列开始于 2021年01月01日,截止于起始日 LeetCode 上共有 1916 道题目,部分是有锁题,我们将先把所有不带锁的题目刷完。
82+
83+
在这个系列文章里面,除了讲解解题思路以外,还会尽可能给出最为简洁的代码。如果涉及通解还会相应的代码模板。
84+
85+
为了方便各位同学能够电脑上进行调试和提交代码,我建立了相关的仓库:https://github.com/SharingSource/LogicStack-LeetCode 。
86+
87+
在仓库地址里,你可以看到系列文章的题解链接、系列文章的相应代码、LeetCode 原题链接和其他优选题解。
88+

0 commit comments

Comments
(0)

AltStyle によって変換されたページ (->オリジナル) /