题解 | #找出字符串中第一个只出现一次的字符#

import sys

for line in sys.stdin:
    line=line.strip()
    result={}
    for i, c in enumerate(line):
        if c not in result:
            result[c]=[i]
        else:
            result[c].append(i)
    
    min_index=len(line)+1
    for k in result:
        if len(result[k])==1 and result[k][0]<min_index:
            min_index=result[k][0]
            
    if min_index==len(line)+1:
        print(-1)
    else:
        print(line[min_index])