問題
One move increases one array value by 1. Make the array nondecreasing: each value must be greater than or equal to the one immediately before it. You may not decrease values or reorder them.
Implement increasing_array(numbers).
Input
numbers: The values in their original order.
Output
Return the minimum total number of unit increments.
制約
1 ≤ length ≤ 200,000. Each value is between 1 and 1,000,000,000. Use a signed 64-bit result.
例
入力：
numbers = [4, 1, 3]
期待される出力：
expected = 4入力：
std::vector<long long> numbers = {4, 1, 3};
期待される出力：
long long expected = 4;入力：
long[] numbers = new long[] {4, 1, 3};
期待される出力：
long expected = 4;解説
Raise 1 to 4 using three moves and 3 to 4 using one move. The result [4, 4, 4] uses four moves.
入力：
numbers = [1, 2, 2, 5]
期待される出力：
expected = 0入力：
std::vector<long long> numbers = {1, 2, 2, 5};
期待される出力：
long long expected = 0;入力：
long[] numbers = new long[] {1, 2, 2, 5};
期待される出力：
long expected = 0;解説
Every value is already at least the preceding value; equal neighbors are allowed.
解き方のヒント
まずは自分で考えてから、ヒントを 1 つずつ開いてみましょう。
ヒント 1
Scan from left to right, because each value only depends on the previous one.
ヒント 2
Whenever a value is too small, raise it just enough to match the running minimum allowed value.
ヒント 3
Track the total increments carefully, since earlier increases affect later comparisons.
目安の計算量
O(n) time, O(1) extra space
参考資料
この課題はCodeUtility用に調整されています。上記の説明と制約に従ってください。