找第一个只出现一次的字符

Status	Submit By	Time	Memory	Language	Code	Submit At
AC	xzh13579	32ms	776 KiB	C++14(O2)	460 Bytes	2025-8-27 22:00:32
AC	陈国瑞	34ms	804 KiB	C++14(O2)	2.1 KiB	2025-7-15 18:19:43
AC	_chjich_	37ms	816 KiB	C++14(O2)	339 Bytes	2025-7-11 10:04:00
AC	钟执墨2026dly	37ms	848 KiB	C++14(O2)	384 Bytes	2026-3-19 21:28:42