Ositus

from collections import deque
from string import ascii_lowercase
from os import read
import cProfile
#
 
s = "-" + input() + "x"
 
 
# s = ["-", read(0, 999999999).decode().strip(), "x"]
# s = ["-", input(), "x"]
# def opt_join(x):
#     global s
#     s = ''.join(x)
#
# opt_join(s)
 
# print(s)
 
 
 
end = len(s) - 1
maxnb = [end+1 for _ in range(end+1)]
maxnb.append(-1)
 
minimum = end + 1
 
 
seen = {ascii_lowercase[i]: end+1 for i in range(26)}
 
last = {i: -1 for i in range(end+2)}
distances = deque()
 
prevdist = 9999999
 
for i in range(end, 0, -1):
    minimum = min(minimum, seen[s[i]])
 
    if minimum < prevdist:
        distances.insert(0, minimum)
        prevdist = minimum
 
    # maxnb[i] = seen[s[i]]
    maxnb[i] = minimum
    seen[s[i]] = i
 
    last[maxnb[i]] = max(last[maxnb[i]], i)
 
seen.clear()
 
def getsum(a, b):
    return sumtable[b] - sumtable[a-1]
 
 
# i+1 indeksointi
sumtable = [0, 1]
 
MOD = 10**9 + 7
 
start = 1
mindist = distances.popleft()
for i in range(2, end+1):
    # check
    if i > mindist:
        start = last[mindist] + 1
        mindist = distances.popleft()
 
    sumtable.append((sumtable[i-1] % MOD + getsum(start, i-1) % MOD) % MOD)
 
 
 
 
 
print((getsum(end, end)) % MOD)
# print(int(getval(end, -1) % MOD))
 
# pr.disable()
# pr.print_stats(sort='time')

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 2, 3

Verdict: ACCEPTED

Test 6

Group: 3

Verdict: ACCEPTED

Test 7

Group: 3

Verdict: ACCEPTED