二维数组中最大子数组之和

一、题目

1.1 要求

1，以指定格式的文本文件形式输入数组。

2，数组由一维变为二维。

3，熟练使用git常用命令将作业签入代码版本控制平台。

1.2 代码

package test;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
 
public class Calculate {
 
    public static void main(String[] args) throws IOException {
 
        Integer[][] c = new Integer[100][];
 
        c = ReadFile("C:\\Users\\Administrator\\Desktop\\my.txt");
        for (int i = 0; i < c.length; i++) {
            for (int j = 0; j < c[0].length; j++) {
                System.out.print(c[i][j] + " ");
            }
            System.out.println();
        }
        System.out.println("max:" + GetMaxSUM(c));
       
    }
 
    public static Integer[][] ReadFile(String str) {
        FileReader file = null;
 
        try {
            file = new FileReader(str);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }
        System.out.println("文件测试数据如下：");
        BufferedReader br = new BufferedReader(file);// 读取文件
        try {
            String line = br.readLine();//读取一行数据
            int lenx = Integer.parseInt(line);// 将数据转化为int类型
            line = br.readLine();

            int leny = Integer.parseInt(line);      String[] sp = null;
            String[][] c = new String[lenx][leny];
            Integer[][] cc = new Integer[lenx][leny];
            int count = 0;
            while ((line = br.readLine()) != null) {// 按行读取
                sp = line.split(" ");// 按空格进行分割
                 for (int i = 0; i < sp.length; i++) {
                    c[count][i] = sp[i];
                }
                count++;
            }
            for (int i = 0; i < lenx; i++) {
                for (int j = 0; j < leny; j++) {
                    cc[i][j] = Integer.parseInt(c[i][j]);
                   
                }
           
            }
            return cc;
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
 
    public static int GetMaxSUM(Integer[][] a) {
        int n = a.length;
        int m = a[0].length;
        // 分块
        Integer[] Max = new Integer[100];
        Integer[] Begin = new Integer[100];
        Integer[] End = new Integer[100];
        Integer[] b = new Integer[100];
        for (int i = 0; i < n; i++) {
            // 按行分组
            for (int j = 0; j < m; j++) {
                b[j] = a[i][j];
 
            }
            MaxIntArray(b, Max, Begin, End, m, i);
        }
 
        int max = Max[0];
        for (int i = 0; i < n - 1; i++) {
            if ((Begin[i] <= End[i + 1] && Begin[i] >= Begin[i + 1])
                    || (End[i] <= End[i + 1] && End[i] >= Begin[i + 1])) {
                max = Max[i + 1] + max;
            } else {
                // 如果不能直接连通，判断代价是否合适
                if (Begin[i] > End[i + 1]) {
                    int t = Begin[i] - End[i + 1];
                    int s = Begin[i];
                    int temp = 0;
                    for (int k = 0; k < t; k++) {
                        temp += a[i + 1][s - k];
                    }
                    if (temp + Max[i + 1] > 0)
                        max = temp + Max[i + 1];
                }
                if (End[i] < Begin[i + 1]) {
                    int t = Begin[i + 1] - End[i];
                    int s = End[i];
                    int temp = 0;
                    for (int k = 0; k < t; k++) {
                        temp += a[i + 1][s + k];
                    }
                    if (temp + Max[i + 1] > 0)
                        max = temp + Max[i + 1];
                }
            }
        }
        return max;
    }
 
    public static void MaxIntArray(Integer[] a, Integer[] max, Integer[] begin, Integer[] end, int n, int index) {
 
        Integer[] Max = new Integer[100];
        Max[0] = 0;
        int i = 0;// 数组下标
        int j = 0;// 最大值数组下标
        int temp = 0;// 中间变量
        // 记录子数组的起始位置和末位
        Integer[] Bg = { -1, -1, -1, -1, -1 };
        Integer[] Ed = new Integer[100];
        while (i < n) {
            if (temp + a[i] >= Max[j]) {
                temp = temp + a[i];
                Max[j] = temp;
                if (Bg[j] == -1)
                    Bg[j] = i;
                Ed[j] = i;
                i++;
            } else if (temp + a[i] < Max[j] && temp + a[i] > 0) {
                temp = temp + a[i];
                i++;
            } else if (temp + a[i] <= 0) {
                i++;
                j++;
                Max[j] = 0;
                temp = 0;
            }
 
        }
        max[index] = Max[0];
        int q = 0;
        for (int k = 0; k <= j; k++) {
            if (Max[k] > max[index]) {
                max[index] = Max[k];
                q = k;
            }
        }
        begin[index] = Bg[q];
        end[index] = Ed[q];
    }
 
}

1.3 结果

my.txt数据如下：

运行结果如下：

二、单元测试

package test;

import static org.junit.Assert.*;
import org.junit.Test;

public class CalculateTest {

    @Test
    public void test1() {
        String str="C:\\Users\\Administrator\\Desktop\\my1.txt";
        Integer[][] c=Calculate.ReadFile(str);
        System.out.println("MaxSUM:"+Calculate.GetMaxSUM(c));
    }
    @Test
    public void test2() {
        String str="C:\\Users\\Administrator\\Desktop\\my2.txt";
        Integer[][] c=Calculate.ReadFile(str);
        System.out.println("MaxSUM:"+Calculate.GetMaxSUM(c));
    }
   
    @Test
    public void test4() {
        String str="C:\\Users\\Administrator\\Desktop\\my4.txt";
        Integer[][] c=Calculate.ReadFile(str);
        System.out.println("MaxSUM:"+Calculate.GetMaxSUM(c));
    }

}