1. Two Sum

https://leetcode.com/problems/two-sum/description/

I. Access control keywords

• For class, only public and default are used.
• default members can be accessed by a class that belongs to the same package.

package & import are used to resolve repeated class names.

Step by step ram analysis

Diffrent languages has diffrent features about parsing parameters. There exists a lot of cofusion around this topic, especailly as people tends to use words like “parsing reference” and “parsing values” trying simplify the problem. Unfortunately, it only leads to more confusion. We need to understand the lower layer.

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Excerpt from https://www.cnblogs.com/kingcat/archive/2012/10/16/2726334.html:

所以我们也可以这样理解,Unicode是用0至65535之间的数字来表示所有字符.其中0至127这128个数字表示的字符仍然跟ASCII完全一样.65536是2的16次方.这是第一步.第二步就是怎么把0至65535这些数字转化成01串保存到计算机中.这肯定就有不同的保存方式了.于是出现了UTF(unicode transformation format),有UTF-8,UTF-16.