【算法很美】多维数组和字符串篇打卡(第三天)

子矩阵的最大累加和

整体代码

package 每日算法学习打卡.算法打卡.七月份.七月三十一号;

import java.util.Arrays;

public class test1 {
    //子矩阵的最大累加和
    public static void main(String[] args) {
        int[][] matrix = {
                {}
        };

        System.out.println(maxSum(matrix));
    }

    public static int maxSum(int[][] matrix) {
        int beginRow = 0;
        if(matrix.length == 0 || matrix[0].length == 0){
            return 0;
        }
        int M = matrix.length;
        int N = matrix[0].length;
        int[] sums = new int[N];
        int max = 0;
        while (beginRow < M) {
            for (int i = beginRow; i < M; i++) {
                for (int j = 0; j < N; j++) {
                    sums[j] += matrix[i][j];
                }
                int t = findByDp(sums);
                if (t > max) {
                    max = t;
                }
            }
            //快速将sums的每个元素都设为0
            Arrays.fill(sums, 0);
            beginRow++;
        }
        return max;
    }

    //使用递推法 来求子数组的最大累加和
    static int findByDp(int[] arr) {

        int sumI = arr[0];
        int maxSum = sumI;
        for (int i = 1; i < arr.length; i++) {
            if(sumI >= 0){
                sumI+= arr[i];
            }else{
                sumI = arr[i];
            }
            if(sumI > maxSum){
                maxSum = sumI;
            }
        }
        return maxSum;
    }
}

矩阵运算-乘法

整体代码

package 每日算法学习打卡.算法打卡.七月份.七月三十一号;

public class test2 {
    public static void main(String[] args) {
        
    }
    /*
     * 矩阵乘法
     * 矩阵1为n*m矩阵，矩阵2为m*p矩阵
     * 结果为n*p矩阵
     *
     * */
    public static long[][] matrixMultiply(long[][] m1, long[][] m2){
        final int n = m1.length;
        final int m = m1[0].length;
        if (m != m2.length) throw new IllegalArgumentException();
        final int p = m2[0].length;

        long[][] result = new long[n][p]; //新矩阵的行数为m1的行数，列数为m2的列数

        for (int i = 0; i < n; i++){//m1的每一行
            for (int j = 0; j < p; j++){//m2的每一列
                for (int k = 0; k < m; k++){
                    result[i][j] += m1[i][k] * m2[k][j];
                }
            }
        }
        return result;
    }

}

检测字符串是否有重复字符

整体代码

package 每日算法学习打卡.算法打卡.七月份.七月三十一号;


import com.sun.xml.internal.ws.util.StringUtils;

public class test3 {
    //检测字符串是否有重复字符
    public static void main(String[] args) {
        String s = "asdff";
        System.out.println(checkDifferent(s));
    }

    public static boolean checkDifferent(String s) {
        if (s == null || s.isEmpty()) {
            return true;
        }
        int[] flag = new int[128];
        for (int i = 0; i < s.length(); i++) {
            int c = (int) s.charAt(i);
            if (flag[c] > 0) return false;
            else flag[c]++;
        }
        return true;
    }
}

反转字符串

整体代码

package 每日算法学习打卡.算法打卡.七月份.七月三十一号;


public class test4 {
    public static void main(String[] args) {
        String s = "adfa";
        System.out.println(reverseString(s));
    }
    public static String reverseString(String s){
        int len = s.length();
        char[] c  = new char[len];
        for(int i =0;i<len;i++){
            c[i] = s.charAt(len-1-i);
        }
        return new String(c);
    }
    //使用java中自带的api来进行翻转
    public static String reverseString1(String a){
        StringBuffer sb = new StringBuffer(a);
        return sb.reverse().toString();
    }
}

变形词

整体代码

package 每日算法学习打卡.算法打卡.七月份.七月三十一号;

import java.util.Arrays;

public class test4 {
    public boolean checkSam(String A,String B){
        int len1=A.length();
        int len2=B.length();
        if(len1 != len2){
            return false;
        }
        char[] arr1 = A.toCharArray();
        char[] arr2 = B.toCharArray();

        Arrays.sort(arr1);
        Arrays.sort(arr2);
        return Arrays.equals(arr1,arr2);
    }
}

替换字符串中的空格

整体代码

package 每日算法学习打卡.算法打卡.七月份.七月三十一号;

import java.sql.SQLOutput;

public class test5 {
    public static void main(String[] args) {
        System.out.println(replaceSpace("hahah adfad adsfas"));
    }
    //第一种方式
    public static String replaceSpace(String s){
        return s.replaceAll("\\s","%20");
    }
    //第二种方式
    public static String replaceSpace1(char[] s){
        int count = s.length;
        for(int i =0;i<s.length;i++){
            if(s[i] == ' '){
                count+=2;
            }
        }
        int p1 = s.length-1;
        int p2 = count-1;
        for(;p1>=0;p1--){
            if(s[p1] == ' '){
                s[p2--] = '0';
                s[p2--] = '2';
                s[p2--] = '%';
            }else{
                s[p2--] = s[p1];
            }
        }
        return new String(s);
    }
}