I wrote a utility class for an nCr problem. It takes a generic array and returns all combinations (without repetition).
import java.util.ArrayList;
public class fooClass {
public static void main(String[] args) {
class Utils {
public int factorial(int n) {
int p = 1;
int i = 1;
while(i <= n) {
p *= i++;
}
return p;
}
public <T> ArrayList<T[]> combinations(T[] array, int r) {
int n = array.length;
int[] vec = new int[r];
int i, j, k, m, o;
for (i = 0; i < vec.length; i++) {
//int j = vec[i];
vec[i] = i;
}
ArrayList<T[]> result = new ArrayList<T[]>();
int total = factorial(n) / (factorial(r) * factorial(n - r));
for (i = 0; i < total; i++) {
T[] combination = (T[])new Object[r];
for (k = 0; k < r; k++) {
combination[k] = array[vec[k]];
}
result.add(combination);
j = r - 1;
if (vec[j] + 1 < n) {
vec[j]++;
} else {
o = j;
while (j-- >= 0) {
if (vec[j] + 1 < n - r - (j + 1)) {
vec[j]++;
m = j + 1;
while (m++ <= o) {
vec[m] = vec[m-1] + 1;
}
break;
} //if end
} //while end
} //if-else end
}
return result;
}
};
Utils utils = new Utils();
String test = "abcde";
ArrayList<char[]> combinations = utils.combinations(test.toCharArray(), 3);
}
}
Now the issue is on the line there I am calling it; the compiler complains when I pass a char[].
The method combinations(T[], int) in the type Utils is not applicable for the arguments (char[], int)
What is the correct way to resolve this?
I think this is because char is a primitive type and T represents an object. If you use Character[] instead of char[], it should work just fine.
char[] chars = test.toCharArray();
Character[] arg = new Character[chars.length];
for (int i = 0; i < chars.length; i++)
arg[i] = chars[i];
ArrayList<Character[]> combinations = utils.combinations(arg, 3);
This copies all of the characters from the char array into the Character array and then passes it to the method.
Related
Problem : You have L, a list containing some digits (0 to 9). Write a function solution(L) which finds the largest number that can be made from some or all of these digits and is divisible by 3. If it is not possible to make such a number, return 0 as the solution. L will contain anywhere from 1 to 9 digits. The same digit may appear multiple times in the list, but each element in the list may only be used once.
Test Cases :
Input:
Solution.solution({3, 1, 4, 1})
Output: 4311
Input:
Solution.solution({3, 1, 4, 1, 5, 9})
Output: 94311
My Program :
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.stream.IntStream;
public class Solution {
static ArrayList<Integer> al = new ArrayList<Integer>();
static ArrayList<Integer> largest = new ArrayList<Integer>();
static int o = 1;
static int po = 0;
static void combinations(String[] digits, String[] data, int start, int end, int index, int r)
{
if (index == r)
{
String temp = "0";
for (int j = 0; j < r; j++)
{
temp = temp + data[j];
// System.out.print(data[j]);
}
Integer d = Integer.parseInt(temp);
al.add(d);
// System.out.println(al);
}
for (int i = start; i <= end && ((end - i + 1) >= (r - index)); i++)
{
data[index] = digits[i];
combinations(digits, data, i + 1, end, index + 1, r);
}
}
static void printCombinations(String[] sequence, int N)
{
String[] data = new String[N];
for (int r = 0; r < sequence.length; r++)
combinations(sequence, data, 0, N - 1, 0, r);
}
static String[] convert(int[] x)
{
String c[] = new String[x.length];
for(int i=0; i < x.length; i++)
{
Integer k = x[i];
if(k==0)
{
o = o * 10;
continue;
}
c[i] = k.toString();
}
// System.out.println(o);
c = Arrays.stream(c).filter(s -> (s != null && s.length() > 0)).toArray(String[]::new);
po = c.length;
// System.out.println("Come"+ Arrays.asList(c));
return c;
}
public static int solution(int[] l) {
if(l.length==0)
return 0;
if(IntStream.of(l).sum()%3==0)
{
String x = "";
Arrays.sort(l);
for (int i = l.length - 1; i >= 0; i--) {
x = x + l[i];
}
return Integer.parseInt(x);
}
printCombinations(convert(l),po);
al.sort(Comparator.reverseOrder());
al.remove(al.size()-1);
al.removeIf( num -> num%3!=0);
if(al.isEmpty())
return 0;
for(int i=0; i< al.size(); i++)
{
Integer n = al.get(i);
printMaxNum(n);
}
// System.out.println(al);
// System.out.println(largest);
return largest.get(0)*o;
}
static void printMaxNum(int num)
{
// hashed array to store count of digits
int count[] = new int[10];
// Converting given number to string
String str = Integer.toString(num);
// Updating the count array
for(int i=0; i < str.length(); i++)
count[str.charAt(i)-'0']++;
// result is to store the final number
int result = 0, multiplier = 1;
// Traversing the count array
// to calculate the maximum number
for (int i = 0; i <= 9; i++)
{
while (count[i] > 0)
{
result = result + (i * multiplier);
count[i]--;
multiplier = multiplier * 10;
}
}
// return the result
largest.add(result);
}
public static void main(String[] args) {
System.out.println(solution(new int[]{9,8,2,3}));
}
}
My Code passes both given test cases and 3 other hidden test cases except one. I tried all possible input combinations but couldn't get to the exact failure. The return type by default is given as int and therefore they would not pass values which give output that does not fit in int. Any other scenario where my code fails?
I'm trying to solve https://leetcode.com/problems/longest-repeating-substring/
I want to use rolling hash to match strings.
However, my codes don't seem to work when I deal with modulo.
For a string with all same characters, the maximum length of repeating substring should be string.length - 1.
public class Main {
public static void main(String[] args) {
String str = "bbbbbbbbbbbbbbbbbbb";
System.out.println(str.length() - 1);
Solution s = new Solution();
System.out.println(s.longestRepeatingSubstring(str));
}
}
class Solution {
public int longestRepeatingSubstring(String S) {
HashSet<Long> h = new HashSet();
long mod = (long)1e7 + 7;
for(int i = S.length() - 1; i >0; i--){
h = new HashSet();
long c = 0;
int j = 0;
for(; j < i; j ++){
c = (c*26 % mod + S.charAt(j) - 'a')% mod;
}
h.add(c);
for(; j < S.length(); j++){
c -= (S.charAt(j - i ) - 'a') * Math.pow(26,i-1)% mod;
c = (c*26 % mod + S.charAt(j) - 'a')% mod;
if(h.contains(c)){
return i;
}
h.add(c);
}
}
return 0;
}
}
Playground for my codes: https://leetcode.com/playground/F4HkxbFQ
We cannot see your original link, we need a password.
The usage of modulo seems to be really complex.
Why not try something like this
class Scratch {
// "static void main" must be defined in a public class.
public static void main(String[] args) {
String str = "bbaaabbbbccbbbbbbzzzbbbbb";
System.out.println(str.length() - 1);
Solution s = new Solution();
System.out.println(s.longestRepeatingSubstring(str));
}
static class Solution {
public int longestRepeatingSubstring(String s) {
int max = -1;
int currentLength = 1;
char[] array = s.toCharArray();
for (int index = 1; index < array.length; index++) {
if (array[index - 1] == array[index]) {
currentLength++;
max = Math.max(max, currentLength);
} else {
currentLength = 1;
}
}
return max;
}
}
}
This method returns an array that contains the positive elements of the parameter array in.
To do that, compute the number of positive elements in the array in and store the obtained value in the variable
nElements of type integer, declare the double array output of size nElements, copy the positive elements
of in into the array output, and return the array output. If all the elements of the array in are non-positive,
your method should return an array of size 1 and the only element of the returned array is assigned the
value -1.
My question here is when I run my program it states Exception in thread "main" java.lang.NegativeArraySizeException and I don't know how to take it out and only return the positive elements.
The Java-Code:
public static double [] partialPositiveArray(double [] in)
{
int nElements = 0;
for(int i = 0; i < in.length; i++)
{
if(in[i] > 0)
{
nElements = (int)in[i];
}
else if(in[i] <= 0)
{
nElements = -1;
}
}
double [] output = new double[nElements];
for(int i = 0; i < in.length; i++)
{
output[i] = nElements;
}
return output;
}
with this code you will add all positive numbers. the sum in this example is 60.7 and for all negative numbers it will write -1 in the negative-array. in this example twice.
Code:
public class NegativeAndPositiveNumbers {
public static void main(String[] args) {
double[] arr = {25.0, -7.0, 10.7, 25.0, -64.0};
System.out.println(partialPositiveArray(arr));
int negative[] = negativeArray(arr);
for (int i = 0; i < negative.length; i++){
System.out.print(negative[i] + " ");
}
}
public static double partialPositiveArray(double[] in) {
double nElements = 0;
for (int i = 0; i < in.length; i++) {
if (in[i] > 0) {
nElements += in[i];
}
}
return nElements;
}
public static int[] negativeArray(double[] in) {
int[] negativeWithZero = new int[in.length];
int index = 0;
for (int i = 0; i < in.length; i++) {
if (in[i] <= 0) {
negativeWithZero[index] = -1;
index++;
}
}
int[] negative = new int[index];
for (int j = 0; j < negative.length; j++){
negative[j] = negativeWithZero[j];
}
return negative;
}
}
I think it could be solved more easily, but it works anyway. I hope everything is clear
public static double [] partialPositiveArray(double [] in) {
return Arrays.stream(in)
.filter(d -> d > 0)
.toArray();
}
You are changing the variable nElements when it is positive you are taking the value from in[ ] array and when it is negative you are changing it to -1.
for(int i = 0; i < in.length; i++)
{
if(in[i] > 0)
{
nElements = (int)in[i];
}
else if(in[i] <= 0)
{
nElements = -1;
}
}
In the array you are passing to the function there seems to be a negative number at end so when control comes across this ,nElements value is -1. After the loop you are instantiating an array with size given as this variable
double [] output = new double[nElements];
Therefore you are getting NegativeArrayIndexException
Solution as per requirement:
public static double [] partialPositiveArray(double [] in)
{
boolean gotPositive=false;
int size=0;
int j=0;
for(int i = 0; i < in.length; i++)
{
if(in[i] >= 0)
{
size++;
gotPositive=true;
}
}
if(size==0 && !gotPositive){
size=1;
}
double [] output = new double[size];
for(int i = 0; i < in.length; i++)
{
if(in[i] >= 0)
{
output[j++]=in[i];
}
}
if(!gotPositive){
output[0]=-1;
}
return output;
}
I was trying to solve a problem based on value and weight. In the task i had to pick out the elements by their value and weight, and find the highest efficiency solution. I receive an answer, however i am having trouble outputting the elements that were used in order to get an answer.
I've tried creating a string in which i place the values, however it gives out an outofbounds error.
public static void main(String[] args) {
String z[] = new String[]{"a","b","c","d","e","f","g","h","l","m"};
int w[] = new int[]{10,2,4,6,8,1,7,11,4,5};
int c[] = new int[]{20,3,5,7,4,1,8,15,8,6};
int maxW = 50;
int n = c.length;
System.out.println("");
int a = Find(w,c,maxW,n,z);
System.out.println("max value is " + a);
}
static int max(int a, int b)
{
if(a>b)
{
return a;
}
return b;
}
public static int Find(int w[],int c[], int maxW,int n, String[]z)
{
int K[][] = new int[n + 1][maxW + 1];
String s = "";
// Build table K[][] in bottom up manner
for (int i = 0; i<= n; i++)
{
for(int j = 0; j<= maxW; j++)
{
if (i == 0 || j == 0)
{
K[i][j] = 0;
}
else if (w[i - 1]<= j)
{
K[i][j] = max(c[i - 1] + K[i - 1][j - w[i - 1]], K[i - 1][j]);
}
else
{
K[i][j] = K[i - 1][j];
}
}
}
return K[n][maxW];
}
}
i want to output the same index element in string z, as the index element that is used to find the efficiancy.
The ideal result would be something like this in a string:
a a a b c d e m
(Just an example)
Thank you in advance.
In this code I am having some problem as I have marked using a loop which is printing some values. I am storing them in an array as mentioned and am trying to print the values in another function. But even after using the global array the value of the array is changing.
I am not able to figure out the problem. Please help me out.
import java.io.*;
import java.util.*;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
// Java program to print all permutations of a
// given string.
public class test3
{
static int[] val = new int[100] ; //array declaration as global
public static void main(String[] args)
{
System.out.println("An incremented value");
for(int i=2;i<=2;i++) {
String p="";
for(int j=0;j<=i;j++) {
for(int m=0;m<j;m++) {
p=p+"&";
}
for(int m=0;m<i-j;m++) {
p=p+"|";
}
printAllPermutations(p);
p="";
}
}
System.out.println();
for(int xy=0;xy<32;xy++)
System.out.print("["+xy+"]"+"="+val[xy]+" "); //trying to print the array
}
static void print(char[] temp) {
String a="";
System.out.println();
for (int i = 0; i < temp.length; i++)
{ System.out.print(temp[i]);
a=a+temp[i];}
System.out.print(" "+"opr:"+temp.length+" ");
final int N = temp.length+1;
/*===================CODE PROBLEM PART START=======================*/
for (int i = 0; i < (1 << N); i++) {
// System.out.println(zeroPad(Integer.toBinaryString(i), N));
String b=zeroPad(Integer.toBinaryString(i), N)+"";
// System.out.println("a: "+a+" b:"+b);
char[] arrayA = b.toCharArray();
char[] arrayB = a.toCharArray();
StringBuilder sb = new StringBuilder();
int ii = 0;
while( ii < arrayA.length && ii < arrayB.length){
sb.append(arrayA[ii]).append(arrayB[ii]);
++ii;
}
for(int j = ii; j < arrayA.length; ++j){
sb.append(arrayA[j]);
}
for(int j = ii; j < arrayB.length; ++j){
sb.append(arrayB[j]);
}
//System.out.println(sb.toString());
try {
ScriptEngineManager sem = new ScriptEngineManager();
ScriptEngine se = sem.getEngineByName("JavaScript");
String myExpression = sb.toString();
// System.out.print(se.eval(myExpression));
val[i]=(int)(se.eval(myExpression)); //inserting array value
System.out.print(val[i]); //NEED TO HAVE THESE VALUES IN THE 1-D ARRAY
// System.out.print(val[i]);
} catch (ScriptException e) {
System.out.println("Invalid Expression");
e.printStackTrace();}
}
/*===================CODE PROBLEM PART END========================*/
//
}
//unchangable = rest of the function
static int factorial(int n) {
int f = 1;
for (int i = 1; i <= n; i++)
f = f * i;
return f;
}
static int calculateTotal(char[] temp, int n) {
int f = factorial(n);
// Building HashMap to store frequencies of
// all characters.
HashMap<Character, Integer> hm =
new HashMap<Character, Integer>();
for (int i = 0; i < temp.length; i++) {
if (hm.containsKey(temp[i]))
hm.put(temp[i], hm.get(temp[i]) + 1);
else
hm.put(temp[i], 1);
}
// Traversing hashmap and finding duplicate elements.
for (Map.Entry e : hm.entrySet()) {
Integer x = (Integer)e.getValue();
if (x > 1) {
int temp5 = factorial(x);
f = f / temp5;
}
}
return f;
}
static void nextPermutation(char[] temp) {
// Start traversing from the end and
// find position 'i-1' of the first character
// which is greater than its successor.
int i;
for (i = temp.length - 1; i > 0; i--)
if (temp[i] > temp[i - 1])
break;
// Finding smallest character after 'i-1' and
// greater than temp[i-1]
int min = i;
int j, x = temp[i - 1];
for (j = i + 1; j < temp.length; j++)
if ((temp[j] < temp[min]) && (temp[j] > x))
min = j;
// Swapping the above found characters.
char temp_to_swap;
temp_to_swap = temp[i - 1];
temp[i - 1] = temp[min];
temp[min] = temp_to_swap;
// Sort all digits from position next to 'i-1'
// to end of the string.
Arrays.sort(temp, i, temp.length);
// Print the String
print(temp);
}
static void printAllPermutations(String s) {
// Sorting String
char temp[] = s.toCharArray();
Arrays.sort(temp);
// Print first permutation
print(temp);
// Finding the total permutations
int total = calculateTotal(temp, temp.length);
for (int i = 1; i < total; i++)
nextPermutation(temp);
}
static String zero(int L) {
return (L <= 0 ? "" : String.format("%0" + L + "d", 0));
}
static String zeroPad(String s, int L) {
return zero(L - s.length()) + s;
}
}
The output that I am getting is
An incremented value
|| opr:2 01111111 //WANT TO STORE THESE 32 VALUES IN 1 D ARRAY
&| opr:2 01010111 // AND PRINT THEM OUT
|& opr:2 00011111
&& opr:2 00000001
[0]=0 [1]=0 [2]=0 [3]=0 [4]=0 [5]=0 [6]=0 [7]=1 [8]=0 [9]=0 [10]=0 [11]=0 [12]=0 [13]=0 [14]=0 [15]=0 [16]=0 [17]=0 [18]=0 [19]=0 [20]=0 [21]=0 [22]=0 [23]=0 [24]=0 [25]=0 [26]=0 [27]=0 [28]=0 [29]=0 [30]=0 [31]=0
what I need to do is to store those 32 values in 1 D array for further operation but while doing it all the array values displays 0 only except [7]. I dont know whats going on here.
Reference types are not bound to local scopes, just because your array is static to the class it does not mean that changing the values in one function will not change the values in the actual array. The reference to your array as a parameter will be a copy, but the reference is still "pointing" on an actual object, which is not a copy bound to your local scope.
If you want to save two different states of the array, you will have to save them yourself.