Java每日一练(20230414) Pow(x, n) 、旋转图像、买卖股票的最佳时机 IV

public class myPow {
    public static class Solution {
        public double myPow(double x, int n) {
            if (n < 0) {
                return 1 / pow(x, -n);
            } else {
                return pow(x, n);
            }
        }
        private double pow(double x, int n) {
            if (n == 0) {
                return 1.0;
            }
            if (n == 1) {
                return x;
            }
            double val = pow(x, n / 2);
            if (n % 2 == 0) {
                return val * val;
            } else {
                return val * val * x;
            }
        }
    }
    public static void main(String[] args) {
        Solution s = new Solution();
        System.out.println(s.myPow(2.0, 10));
        System.out.println(s.myPow(2.1, 3));
        System.out.println(s.myPow(2.0, -2));
    }
}

import java.util.*;
public class rotate {
    public static class Solution {
        public void rotate(int[][] matrix) {
            int len = matrix.length;
            int le = len - 1;
            for (int i = 0; i < len / 2; i++) {
                for (int j = 0; j < (len + 1) / 2; j++) {
                    int temp = matrix[i][j];
                    matrix[i][j] = matrix[le - j][i];
                    matrix[le - j][i] = matrix[le - i][le - j];
                    matrix[le - i][le - j] = matrix[j][le - i];
                    matrix[j][le - i] = temp;
                }
            }
        }
    }
    public static void main(String[] args) {
        Solution s = new Solution();
        int[][] matrix = {{1,2,3},{4,5,6},{7,8,9}};
        s.rotate(matrix);
        System.out.println(Arrays.deepToString(matrix));
        int[][] matrix2 = {{5,1,9,11},{2,4,8,10},{13,3,6,7},{15,14,12,16}};
        s.rotate(matrix2);
        System.out.println(Arrays.deepToString(matrix2));
        int[][] matrix3 = {{1}};
        s.rotate(matrix3);
        System.out.println(Arrays.deepToString(matrix3));
        int[][] matrix4 = {{1,2},{3,4}};
        s.rotate(matrix4);
        System.out.println(Arrays.deepToString(matrix4));
    }
}

class Solution {
    public void rotate(int[][] matrix) {
        int len = matrix.length;
        for (int i = 0; i < len / 2; i++) {
          int di = len - i - 1;
            for (int j = 0; j < (len + 1) / 2; j++) {
                int temp = matrix[i][j];
                int dj = len - j - 1;
                matrix[i][j] = matrix[dj][i];
                matrix[dj][i] = matrix[di][dj];
                matrix[di][dj] = matrix[j][di];
                matrix[j][di] = temp;
            }
        }
    }
}

import java.util.*;
public class maxProfit {
    public static class Solution {
        public int maxProfit(int k, int[] prices) {
            if (k < 1)
                return 0;
            if (k >= prices.length / 2)
                return greedy(prices);
            int[][] t = new int[k][2];
            for (int i = 0; i < k; ++i)
                t[i][0] = Integer.MIN_VALUE;
            for (int p : prices) {
                t[0][0] = Math.max(t[0][0], -p);
                t[0][1] = Math.max(t[0][1], t[0][0] + p);
                for (int i = 1; i < k; ++i) {
                    t[i][0] = Math.max(t[i][0], t[i - 1][1] - p);
                    t[i][1] = Math.max(t[i][1], t[i][0] + p);
                }
            }
            return t[k - 1][1];
        }
        private int greedy(int[] prices) {
            int max = 0;
            for (int i = 1; i < prices.length; ++i) {
                if (prices[i] > prices[i - 1])
                    max += prices[i] - prices[i - 1];
            }
            return max;
        }
    }
    public static void main(String[] args) {
        Solution s = new Solution();
        int[] prices = {2,4,1};
        System.out.println(s.maxProfit(2, prices));
        int[] prices2 = {3,2,6,5,0,3};
        System.out.println(s.maxProfit(2, prices2));
    }
}