poj2250

package middle;


import java.io.BufferedInputStream;
import java.util.Scanner;

/**
 *poj2250 middle
 * 最长公共子序列
 * 看了网上牛人的动态规划法，太强了！！！
 * 两个序列的最长公共子序列包含了这两个序列的前缀的最长公共子序列。因此，最长公共子序列问题具有最优子结构性质。
 * @author NC
 */
public class Poj2250 {

    private static final int MAXLEN = 101;
    private static int[][] c = new int[MAXLEN][MAXLEN];
    private static int[][] b = new int[MAXLEN][MAXLEN];

    public static void main(String[] args) {
        Scanner scan = new Scanner(new BufferedInputStream(System.in));
        while (scan.hasNext()) {
            String s1 = "", s2 = "";
            while (scan.hasNext()) {
                String s = scan.nextLine();
                if (s.startsWith("#")) {
                    break;
                }
                s.trim();
                s1 = s1 + s + " ";
            }
            while (scan.hasNext()) {
                String s = scan.nextLine();
                if (s.startsWith("#")) {
                    break;
                }
                s.trim();
                s2 = s2 + s + " ";
            }
            String[] ss1 = s1.trim().split(" ");
            String[] ss2 = s2.trim().split(" ");
            lcsLength(ss1, ss2);
            printLCS(ss1, ss1.length, ss2.length);
        }
    }

    public static void lcsLength(String[] x, String[] y) {
        for (int i = 0; i <= x.length; i++) {
            c[i][0] = 0;
        }
        for (int i = 0; i <= y.length; i++) {
            c[0][i] = 0;
        }
        for (int i = 1; i <= x.length; i++) {
            for (int j = 1; j <= y.length; j++) {
                if (x[i - 1].equals(y[j - 1])) {
                    c[i][j] = c[i - 1][j - 1] + 1;
                    b[i][j] = 0;
                } else if (c[i - 1][j] >= c[i][j - 1]) {
                    c[i][j] = c[i - 1][j];
                    b[i][j] = 1;
                } else {
                    c[i][j] = c[i][j - 1];
                    b[i][j] = -1;
                }
            }
        }
    }

    public static void printLCS(String[] x, int m, int n) {
        int i = m;
        int j = n;
        if (i == 0 || j == 0) {
            return;
        }
        if (b[i][j] == 0) {
            printLCS(x, i - 1, j - 1);
            System.out.print(x[i - 1] + " ");
        } else if (b[i][j] == 1) {
            printLCS(x, i - 1, j);
        } else {
            printLCS(x, i, j - 1);
        }
    }
}