阿里笔试——获取格子编号

def getMark(k):
    sum=0
    for i in range(1, 100000):
        for j in range(1, i+1):
            if j <10:
                sum +=1
            elif j<100:
                sum += 2
            elif j <1000:
                sum += 3
            elif j <10000:
                sum += 4
            elif j <100000:
                sum += 5
            else:
                sum+=6
            if (sum-k) <len(str(j)):
                mark=0
                for s in str(j):
                    mark+=1
                    l=len(str(j))-mark
                    if (sum-k) == l:
                        return s