LeetCode 2158: Amount of New Area Painted Each Day Solution

Master LeetCode problem 2158 (Amount of New Area Painted Each Day), a hard challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2158. Amount of New Area Painted Each Day

Hard

Array Segment Tree Ordered Set

Problem Explanation

Explanation:

The problem asks us to calculate the amount of new area painted each day given a list of painted cells. The new area painted each day is defined as the cells that were not painted the previous day but are painted today.

To solve this problem, we can iterate through the list of painted cells and maintain a set to keep track of the cells that have been painted. We can then iterate through the list of painted cells each day and compare it with the set of painted cells from the previous day to calculate the new area painted each day.

Algorithm:

Initialize an empty set painted_cells to store the painted cells.
Initialize a variable new_area to store the amount of new area painted each day.
Iterate through the list of painted cells:
- For each day, calculate the new area painted by subtracting the previous day's painted cells from the current day's painted cells.
- Add the new area painted each day to the new_area.
- Update the set painted_cells with the current day's painted cells for the next iteration.

Time Complexity: O(n) where n is the total number of painted cells. Space Complexity: O(n) for storing the painted cells in the set.

Solution Code

public int[] amountOfNewAreaPaintedEachDay(int[][] painted) {
    Set<String> paintedCells = new HashSet<>();
    int[] newAreaPaintedEachDay = new int[painted.length - 1];
    
    for (int i = 1; i < painted.length; i++) {
        Set<String> currentDayPainted = new HashSet<>();
        for (int j = 0; j < painted[i].length; j++) {
            currentDayPainted.add(painted[i][j] + "-" + painted[i][j + 1]);
        }
        Set<String> newAreaPainted = new HashSet<>(currentDayPainted);
        newAreaPainted.removeAll(paintedCells);
        paintedCells.addAll(currentDayPainted);
        
        newAreaPaintedEachDay[i - 1] = newAreaPainted.size();
    }
    
    return newAreaPaintedEachDay;
}

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