package com.chao.dynamicProgramming;

public class LCSL {

    //lcsl()方法用來計算最長公共子序列的長度
    public static int  lcsl(int[][] c, int[][]b, String str1, String str2){

        //int[][] c = new int[str1.length()+1][str2.length()+1];//二維陣列存放當前最長子序列的長度
        //int[][] b = new int[str1.length()+1][str2.length()+1];//記錄最優策略來源
 


        //初始化c[][]的第一行和第一列都為0
        for(int row = 0; row <= str2.length(); row++)
            c[0][row] = 0;
        for(int column = 0; column <= str1.length(); column++)
            c[column][0] = 0;

        //初始化b[][]的第一行和第一列都為0
        for(int row = 0; row <= str2.length(); row++)
            b[0
 
][row] = 0;
        for(int column = 0; column <= str1.length(); column++)
            b[column][0] = 0;

        //計算最長公共子串的長度
        for(int i = 1; i <= str1.length(); i++){
            for(int j = 1; j <= str2.length(); j++){
                if(str1.charAt(i-1) == str2.charAt(j-1)){
                    c[i][j] = c[i-1
 
][j-1] + 1;
                    b[i][j] = 1;
                }else if((str1.charAt(i-1) != str2.charAt(j-1)) && c[i][j-1] >= c[i-1][j]){
                    c[i][j] = c[i][j-1];
                    b[i][j] = 2;
                }else if((str1.charAt(i-1) != str2.charAt(j-1)) && c[i][j-1] < c[i-1][j]){
                    c[i][j] = c[i-1][j];
                    b[i][j] = 3;
                }
            }
        }
        return c[str1.length()][str2.length()];
    }

    //輸出最長的公共子串
    public static void printLCS(int i, int j, String str1, int[][] b){
        if(i == 0 || j == 0)
            return;
        if(b[i][j] == 1){
            printLCS(i-1, j-1, str1, b);
            System.out.println(str1.charAt(i-1));
        }else if(b[i][j] == 2){
            printLCS(i, j-1, str1, b);
        }else{
            printLCS(i-1, j, str1, b);
        }
    }

    public static void main(String[] args) {
        String str1 = "BDCABA";
        String str2 = "ABCBDAB";
        int[][] c = new int[str1.length()+1][str2.length()+1];//二維陣列存放當前最長子序列的長度
        int[][] b = new int[str1.length()+1][str2.length()+1];//記錄最優策略來源
        System.out.println(lcsl(c, b, str1, str2));
        printLCS(str1.length(), str2.length(), str1, b);
    }
}