1622. Fancy Sequence

https://leetcode.com/problems/fancy-sequence

Description

Write an API that generates fancy sequences using the append, addAll, and multAll operations.

Implement the Fancy class:

• Fancy() Initializes the object with an empty sequence.

• void append(val) Appends an integer val to the end of the sequence.

• void addAll(inc) Increments all existing values in the sequence by an integer inc.

• void multAll(m) Multiplies all existing values in the sequence by an integer m.

• int getIndex(idx) Gets the current value at index idx (0-indexed) of the sequence modulo 109 + 7. If the index is greater or equal than the length of the sequence, return -1.

Example 1:

**Input**
["Fancy", "append", "addAll", "append", "multAll", "getIndex", "addAll", "append", "multAll", "getIndex", "getIndex", "getIndex"]
[[], [2], [3], [7], [2], [0], [3], [10], [2], [0], [1], [2]]
**Output**
[null, null, null, null, null, 10, null, null, null, 26, 34, 20]
**Explanation**
Fancy fancy = new Fancy();
fancy.append(2);   // fancy sequence: [2]
fancy.addAll(3);   // fancy sequence: [2+3] -> [5]
fancy.append(7);   // fancy sequence: [5, 7]
fancy.multAll(2);  // fancy sequence: [5*2, 7*2] -> [10, 14]
fancy.getIndex(0); // return 10
fancy.addAll(3);   // fancy sequence: [10+3, 14+3] -> [13, 17]
fancy.append(10);  // fancy sequence: [13, 17, 10]
fancy.multAll(2);  // fancy sequence: [13*2, 17*2, 10*2] -> [26, 34, 20]
fancy.getIndex(0); // return 26
fancy.getIndex(1); // return 34
fancy.getIndex(2); // return 20

Constraints:

• 1 <= val, inc, m <= 100

• 0 <= idx <= 105

• At most 105 calls total will be made to append, addAll, multAll, and getIndex.

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