Given n non-negative integers a1, a2, …, an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a container, such that the container contains the most water.

Note: You may not slant the container.

    public int maxArea(int[] height) {
        int maxArea = 0;
        int left = 0;
        int right = height.length - 1;
        while (left < right) {
            maxArea = Math.max(maxArea, calculateArea(height, left, right));
            if (height[left] < height[right]) {
                left++;
            } else {
                right--;
            }
        }
        return maxArea;
    }

    public int calculateArea(int[] height, int left, int right) {
        return Math.abs(right - left) * Math.min(height[left], height[right]);
    }

Note:

For any container, its volume depends on the shortest board.

Two-pointer scan. And always move with shorter board index.

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You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Follow up:
Could you do this in-place?

public class Solution {
    public void rotate(int[][] matrix) {
        int n = matrix.length;
        if (n <= 1 || matrix.length <= 1 || n != matrix.length) {
            return;
        }
        int mid = (n - 1) / 2;
        int offset = 0;
        while (offset <= mid) {
            for (int i = offset; i < n - 1 - offset; i++) {
                int tmp = matrix[offset][i];
                matrix[offset][i] = matrix[n - 1 - i][offset];
                matrix[n - 1 - i][offset] = matrix[n - 1 - offset][n - 1 - i];
                matrix[n - 1 - offset][n - 1 - i] = matrix[i][n - 1 - offset];
                matrix[i][n - 1 - offset] = tmp;
            }
            offset++;
        }

    }
}

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