算法复习___二分_矩阵连乘

IoUtil接口：

import java.util.List;


public interface IoUtil {
    public int getInt();
    public List<Integer> getIntList(int n);
    public int[] getIntArray(int n);
    public double getDouble();
    public List<Double> getDoubleList(int n);
    public double[] getDoubleArray(int n);
    
}

IoUtilImpl接口实现类：

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;


public class IoUtilImpl implements IoUtil {
    public static Scanner cin;
    static{
        cin = new Scanner(System.in);
    }
    @Override
    public double getDouble() {
        return cin.nextDouble();
    }

    @Override
    public List<Double> getDoubleList(int n) {
        ArrayList<Double> list = new ArrayList<Double>();
        for(int i = 0; i < n; i++){
            list.add(cin.nextDouble());
        }
        return list;
    }

    @Override
    public int getInt() {
        return cin.nextInt();
    }

    @Override
    public List<Integer> getIntList(int n) {
        ArrayList<Integer> list = new ArrayList<Integer>();
        for(int i = 0; i < n; i++){
            list.add(cin.nextInt());
        }
        return list;
    }

    @Override
    public double[] getDoubleArray(int n) {
        double[] m = new double[n];
        for(int i = 0; i < n; i++){
            m[i] = cin.nextDouble();
        }
        return m;
    }

    @Override
    public int[] getIntArray(int n) {
        int[] m = new int[n];
        for(int i = 0; i < n; i++){
            m[i] = cin.nextInt();
        }
        return m;
    }

}

二分主类:

import java.util.Arrays;


public class 二分 {
    public static int maxi, minj;
    public static boolean erFen(int[] m, int l, int r, int x){
        int mid;
        while(l <= r){
            mid = (l + r) / 2 ;
            if(x == m[mid]){
                maxi = minj = mid;
                return true;
            }
            if(x <= m[mid])
                r = mid - 1;
            else
                l = mid + 1;
        }
        maxi = l - 1;
        minj = l;
        return false;
    }
    public static void main(String[] args) {
        int n;
        int a[];
        int x;
        IoUtilImpl util;
        util= new IoUtilImpl();
        System.out.println("请输入数组长度n:");
        n = util.getInt();
        System.out.println("请输入 " + n + " 个数组元素");
        a = util.getIntArray(n);
        Arrays.sort(a);
        while(true){
            System.out.println("请输入要查找的元素x（x=0 时退出）");
            x = util.getInt();
            if(x == 0){
                break;
            }
            if(erFen(a, 0, n - 1, x)){
                System.out.println("可以查到元素 " + x);
                System.out.println("该元素在第 " + maxi + " 个位置");
            }else{
                System.out.println("不能查到元素" + x);
                System.out.println("元素  " + x + " 在位置 " + maxi + " 和位置 " + minj + " 之间");
            }
        }
        
    }
}

 矩阵连乘：不知道对不对，好像错了，先放着：

import java.util.Scanner;


class Matrix{
    int l;
    int r;
    static Scanner cin;
    static{
        cin = new Scanner(System.in);
    }
    public Matrix() {
        
    }
    public Matrix(int l, int r){
        this.l = l;
        this.r = r;
    }
    public void input(){
        l = cin.nextInt();
        r = cin.nextInt();
    }
}
public class 矩阵连乘 {
    public static Matrix[] matrix;
    public static int[][] m;
    public static int n;
    public static IoUtilImpl util;
    static{
        util = new IoUtilImpl();
    }
    static void init(){
        for(int i = 0; i < n; i++){
            m[i][i] = 0;
            int l = matrix[i].l, mid, r;
            int sum = 0;
            for(int j = i + 1; j < n; j++){
                mid = matrix[j].l;
                r = matrix[j].r;
                sum += l * mid * r;
                m[i][j] = m[j][i] = sum;
            }
        }
    }
    public static void main(String[] args) {
        System.out.println("请输入矩阵个数n：");
        n = util.getInt();
        matrix = new Matrix[n];
        m = new int[n][n];
        System.out.println("请输入这n个矩阵：");
        for(int i = 0; i < n; i++){
            Matrix x = new Matrix();
            x.input();
            matrix[i] = x;
        }
        init();
        for(int i = 0; i < n; i++){
            for(int j = i + 1; j < n; j++){
                for(int k = i; k < j; k++){
                    m[i][j] = Math.min(m[i][j], m[i][k] + m[k + 1][j] + matrix[i].l*matrix[k].r*matrix[j].l);
                }
            }
        }
        System.out.println("最小连乘次数是： " + m[0][n - 1]);
    }
}