CCF JPEG 解码 (Java题解)

一、题目

题目链接：ccf官网

二、题解（Java版）

做了好几道第三题这种模拟大题，第一次在不看其他人题解的情况下拿到满分，好激动啊啊啊啊

import java.util.Scanner;

public class Main {

	static int[][] Q = new int[8][8];
	static int[][] M = new int[8][8]; // 对M1进行操作，M存原始数据，M1是结果
	static double[][] M1 = new double[8][8];

	// 离散变换
	static void liSan(int i, int j) {
		double mij = 0L;
		for (int u = 0; u < 8; u++) {
			for (int v = 0; v < 8; v++) {
				double temp = M[u][v] * Math.cos(Math.PI / 8 * u * (i + 0.5))
						* Math.cos(Math.PI / 8 * v * (j + 0.5));
				if (u == 0 && v == 0) {
					mij += 0.5 * temp;
				} else if ((u != 0 && v == 0) || (u == 0 && v != 0)) {
					mij += Math.sqrt(0.5) * temp;
				} else {
					mij += 1.0 * temp;
				}
			}

		}
		mij /= 4;
		M1[i][j] = mij;
	}

	static void four() {
		for (int i = 0; i < 8; i++) {
			for (int j = 0; j < 8; j++) {
				M[i][j] *= Q[i][j];
				M1[i][j] = M[i][j];  //M复制到M1
			}
		}
	}

	static void five() {
		for (int i = 0; i < 8; i++) {
			for (int j = 0; j < 8; j++) {
				liSan(i, j);
			}
		}
	}

	static void six() {
		for (int i = 0; i < 8; i++) {
			for (int j = 0; j < 8; j++) {
				M1[i][j] += 128;
				if (M1[i][j] % 1 >= 0.5) {
					M[i][j] = (int) (M1[i][j] + 0.5);
					if (M[i][j] > 255) {
						M[i][j] = 255;
					}
					if (M[i][j] < 0) {
						M[i][j] = 0;
					}
				} else {
					M[i][j] = (int) M1[i][j];
					if (M[i][j] > 255) {
						M[i][j] = 255;
					}
					if (M[i][j] < 0) {
						M[i][j] = 0;
					}
				}
			}
		}
	}

	static void cout() {
		for (int i = 0; i < 8; i++) {
			for (int j = 0; j < 8; j++) {
				System.out.print(M[i][j] + " ");
			}
			System.out.println();
		}
	}

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		for (int i = 0; i < 8; i++) {
			for (int j = 0; j < 8; j++) {
				Q[i][j] = in.nextInt();
			}
		}
		int n = in.nextInt();
		int T = in.nextInt();
		int[] m = new int[n];
		for (int i = 0; i < n; i++) {
			m[i] = in.nextInt();
		}
		boolean up = true;
		for (int i = 0, j = 0, k = 0; k < n; k++) {
//			System.out.println("i= "+i+" j= "+j);
			M[i][j] = m[k];
			// 更新游标
			if (i == 0 || j == 0 || i == 7 || j == 7) {
				if (i == 0 && j % 2 == 0) {
					j++;
				} else if (i == 0 && j % 2 == 1) {
					i++;
					j--;
					up = false;
				} else if (j == 0 && i % 2 == 1 && i != 7) {
					i++;
				} else if (j == 0 && i % 2 == 0) {
					i--;
					j++;
					up = true;
				} else if (i == 7 || i + j > 7) { // 从左下角开始反转
					if (i == 7 && j % 2 == 0) {
						j++;
					} else if (i == 7 && j % 2 == 1) {
						i--;
						j++;
						up = true;
					} else if (j == 7 && i % 2 == 1) {
						i++;
					} else if (j == 7 && i % 2 == 0) {
						i++;
						j--;
						up = false;
					}
				}
			} else { // 不在正方形一周时的情况
				if (!up) {
					i++;
					j--;
				} else {
					i--;
					j++;
				}
			}
		}
		if (T == 0) {
			cout();
		} else if (T == 1) {
			four();
			cout();
		} else {
			four();
			five();
			six();
			cout();
		}
	}
}