The Integers and the Real Numbers

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The Integers and the Real Numbers

以上我們談了一些邏輯的基礎,接下來我們會談一些數學的基礎,也就是整數與實數系統.其實我們已經用了很多,非正式地,接下來我們會正式地討論他們. 要建構實數系統的一個方法就是利用公理跟集合論來建構. 首先我們需要從集合論出發,定義在 set $A$ 上的二元運算子(binary operator): Def. $$f: A times A rightarrow A$$ 我們在描述一個二元運算子的時候並不會如同以往的函數一樣, $f(a, a')$,而是會把運算子寫在中間, $afa'$.一…

PAT1120: Friend Numbers

1120. Friend Numbers (20) 时间限制 400 ms 内存限制 65536 kB 代码长度限制 16000 B 判题程序 Standard 作者 CHEN, Yue Two integers are called "friend numbers" if they share the same sum of their digits, and the sum is their "friend ID". For example, 123 and 5…

PAT 1120 Friend Numbers

1120 Friend Numbers (20 分) Two integers are called "friend numbers" if they share the same sum of their digits, and the sum is their "friend ID". For example, 123 and 51 are friend numbers since 1+2+3 = 5+1 = 6, and 6 is their friend…

A1120. Friend Numbers

Two integers are called "friend numbers" if they share the same sum of their digits, and the sum is their "friend ID". For example, 123 and 51 are friend numbers since 1+2+3 = 5+1 = 6, and 6 is their friend ID. Given some numbers, you…

PAT A1120 Friend Numbers （20 分）——set

Two integers are called "friend numbers" if they share the same sum of their digits, and the sum is their "friend ID". For example, 123 and 51 are friend numbers since 1+2+3 = 5+1 = 6, and 6 is their friend ID. Given some numbers, you…

Lintcode521-Remove Duplicate Numbers in Array-Easy

Description Given an array of integers, remove the duplicate numbers in it. You should: Do it in place in the array. Move the unique numbers to the front of the array. Return the total number of the unique numbers. Example 1: Input: nums = [1,3,1,4,4…