C++ Python C速解Leetcode 344 Reverse String

C++ Python C速解Leetcode 344  Reverse String

交換索引對 (i, n-1-i)。在C的實作中，交換並沒有使用額外的空間，只是透過xor！

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So swap the pairs of index (i, n-1-i). In the implementation by C, swap doesn't use extra space just by xor!

[codes on Leetcode]https://leetcode.com/problems/reverse-string/solutions/5242835/easy-swap-pairs-swap-using-xor-1-liner/