题解 | #小苯的区间选数#

思路很简单，直接上代码

from sys import stdin
input = stdin.readline
t = int(input())
def sumdigit(x):
    return sum(int(i) for i in str(x))
def f(ltrue,rtrue,temp):
    tempmax = 0
    if rtrue-ltrue <= 20:
        for i in range(ltrue,rtrue+1):
            tempmax = max(tempmax,sumdigit(i))
        print(tempmax+temp)
        return
    else:
        if len(str(ltrue))<len(str(rtrue)):
            print(max(9*(len(str(rtrue))-1)+int(str(rtrue)[0])-1,sumdigit(str(rtrue)))+temp)
            return
        else:
            if str(rtrue)[0] != str(ltrue)[0]:
                print(max(9 * (len(str(rtrue)) - 1) + int(str(rtrue)[0]) - 1, sumdigit(str(rtrue)))+temp)
                return
            else:
                f(int(str(ltrue)[1:]),int(str(rtrue)[1:]),temp+int(str(ltrue)[0]))
for _ in range(t):
    l1,r1,l2,r2 = map(int,input().split())
    ltrue = l1+l2
    rtrue = r1+r2
    f(ltrue,rtrue,0)