题解 | 【模板】双指针

n = int(input())
arr = list(map(int, input().split()))

res = []
occ = [-1] * n
maxLen = -1
i = 0
arr.append(arr[-1])  # Sentinel
n += 1
for j in range(n):
    x = arr[j]
    if occ[x] >= i:
        curLen = j - i
        if curLen > maxLen:
            maxLen = curLen
            res = [(i+1, j)]
        elif curLen == maxLen:
            res.append((i+1, j))
        i = occ[x] + 1  # Jump
    occ[x] = j

print(len(res))
print('\n'.join(f"{t[0]} {t[1]}" for t in sorted(res)))