So the start is:
Random r = new Random();
int[,] mas = new int[4, 5];
for (int i = 0; i < mas.GetLength(0); i++)
{
for (int j = 0; j < mas.GetLength(1); j++)
{
mas[i, j] = r.Next(1, 10);
Console.Write("{0}\t", mas[i, j]);
}
Console.WriteLine();
}
Console.WriteLine();
Looks something like
4 3 5 6 2
3 5 6 7 4
2 3 4 5 5
2 3 4 5 6
What i i need is to get 0 above the diagonal.
4 0 0 0 0
3 5 0 0 0
2 3 4 0 0
2 3 4 5 0
This is what i've got so far, no what i need , but atleast got some diagonal and some 0's.
for (int i = 0; i < mas.GetLength(0); i++)
{
for (int j = i; j < mas.GetLength(1); j++)
{
mas[i, j] = 0;
Console.Write("{0}\t", mas[i, j]);
}
Console.WriteLine();
}
If you want to do everything in one go, you could do this:
Random r = new Random();
int[,] mas = new int[4, 5];
for (int i = 0; i < mas.GetLength(0); i++)
{
for (int j = 0; j < mas.GetLength(1); j++)
{
mas[i, j] = j > i ? 0 : r.Next(1, 10);
Console.Write("{0}\t", mas[i, j]);
}
Console.WriteLine();
}
Console.WriteLine();
Otherwise, your second section needs to be:
for (int i = 0; i < mas.GetLength(0); i++)
{
for (int j = i; j < mas.GetLength(1); j++)
{
if(j > i) mas[i, j] = 0;
Console.Write("{0}\t", mas[i, j]);
}
Console.WriteLine();
}
try this one (inside the inner loop):
if(j > i ) mas[i, j] = 0; // column number > row number, above diagonal
or the (better) alternative (inside the outer loop):
for (int j = i+1; j < mas.GetLength(1); j++)
{
mas[i, j] = 0;
Console.Write("{0}\t", mas[i, j]);
}
Using Linq
Random r = new Random();
//int[,] mas = new int[4, 5];
int[][] mas = new int[4][];
for (int i = 0; i < mas.Length; i++)
{
mas[i] = new int[5];
for (int j = 0; j < mas[i].Length; j++)
{
mas[i][j] = r.Next(1, 10);
Console.Write("{0}\t", mas[i][j]);
}
Console.WriteLine();
}
for (int i = 0; i < mas.Length; i++)
{
mas[i] = mas[i].Select((c, ind) =>
{
if (ind > i)
c = 0;
return c;
}).ToArray();
}
Related
i´d like to build a pascal´s triangle as a square matrix in c# like this.
1 0 0 0 0
1 1 0 0 0
1 2 1 0 0
1 3 3 1 0
1 4 6 4 1
But the following code didn´t perform, could you please help me?
Console.Write("Size of Matrix: ");
int size = Convert.ToInt32(Console.ReadLine());
int[,] pascal = new int[size, size];
for (int i = 0; i < pascal.GetLength(0);i++)
{
for (int j = 0; j < pascal.GetLength(1); j++)
{
if (j > i )
{
pascal[i, j] = 0;
}
if (i == j || j == 0)
{
pascal[i, j] = 1;
}
if (i !=j)
{
pascal[i, j] = pascal[i - 1, j - 1] + pascal[i - 1, j];
}
Console.Write($"{pascal[i,j ],5 }");
}
Console.WriteLine();
}
thx
You are forgot else if and rewrite data if (i != j)
Console.Write("Size of Matrix: ");
int size = Convert.ToInt32(Console.ReadLine());
int[,] pascal = new int[size, size];
for (int i = 0; i < size; i++)
{
for (int j = 0; j < size; j++)
{
if (i == j || j == 0)
{
pascal[i, j] = 1;
}
else if (j > i)
{
pascal[i, j] = 0;
}
else if (i != j)
{
pascal[i, j] = pascal[i - 1, j - 1] + pascal[i - 1, j];
}
Console.Write($"{pascal[i, j],5 }");
}
Console.WriteLine();
}
Your problem is your ifs, need to be else if otherwise you will be trying to reference negative indexes in the array with pascal[i - 1, j - 1] etc.
for (int i = 0; i < pascal.GetLength(0); i++)
{
for (int j = 0; j < pascal.GetLength(1); j++)
{
if (j > i)
pascal[i, j] = 0;
else if (i == j || j == 0)
pascal[i, j] = 1;
else if (i != j)
pascal[i, j] = pascal[i - 1, j - 1] + pascal[i - 1, j];
Console.Write($"{pascal[i, j],5}");
}
Console.WriteLine();
}
Another way you could achieve this is with good old fashioned math
for (var i = 0; i < rows; i++)
for (var j = 0; j <= i; j++)
if (j != 0 && i != 0)
pascal[i, j] = val = val * (i - j + 1) / j;
else
pascal[i, j] = 1;
To Output
for (var i = 0; i < rows; i++)
{
for (var j = 0; j < rows; j++)
Console.Write($"{pascal[i, j]} ");
Console.WriteLine();
}
A new array always contain zeros. You could seed the 1's outside the loops, then only loop through the rest.
I would also separate the construction of the array, from the printing method. If you only wanted to print it, you'd only need one array.
int[,] pascal = new int[size, size];
pascal[0, 0] = 1;
for (int i = 1; i < size; i++)
{
pascal[i, 0] = pascal[i, i] = 1;
for (int j = 1; j <= i - 1; j++)
pascal[i, j] = pascal[i - 1, j - 1] + pascal[i - 1, j];
}
To help to grasp this dynamic programming concept the following is my recursive solution.
for(var i = 0; i < 5; ++i)
{
for(var j = 0; j < i + 1; ++j)
{
Console.Write($"{p(i, j)} ");
}
Console.WriteLine();
}
static int p(int i, int j)
=> (j == 0 || i == j)
? 1
: p(i - 1, j) + p(i - 1, j - 1);
I'm a new student having a bit of trouble with this assignment, but the powerpoint notes and other online guides don't seem to help. If anyone can give me a pointer it would be much appreciated!
private static int[,] GenerateTT(int size)
{
int[,] table = new int[size,size];
for (int i = 1; i < size+1; i++)
{
for (int j = 1; j < i+1; j++)
{
table[i-1, j-1] = i * j;
}
}
return table;
}
private static void DisplayTT(int[,] table)
{
Console.WriteLine();
Console.WriteLine("Here is the times table for that size:");
Console.WriteLine();
for (int i = 1; i <= table.Length; i++)
{
for (int j = 1; j <= i; j++)
{
Console.Write("{0}\t", table[i-1, j-1]);
}
Console.WriteLine("\n");
}
Console.WriteLine();
}
The output is supposed to be like this (if you enter 4 for example):
1 2 3 4
2 4 6 8
3 6 9 12
4 8 12 16
But what I'm getting is this, plus it crashes at DisplayTT(table):
1
2 4
3 6 9
4 8 12 16
here's the relevant part of the Main method if it helps.
int size = GetValue("Please enter the size (4-20) of the times table: ", 4, 20);
Console.WriteLine();
int[,] table = GenerateTT(size);
DisplayTT(table);
You can use GetLength(X) Property for multi dimensional arrays where X is index of dimension.
for (int i = 0; i < table.GetLength(0); i++)
{
for (int j = 0; j < table.GetLength(1); j++)
{
Console.Write("{0}\t", table[i, j]);
}
Console.WriteLine("\n");
}
You should change the inner loop hi-bound:
private static int[,] GenerateTT(int size)
{
int[,] table = new int[size,size];
for (int i = 1; i < size+1; i++)
{
for (int j = 1; j < i+1; j++) // <-- change i+1 to size+1
{
table[i-1, j-1] = i * j;
}
}
return table;
}
I'd rather keep the loops start from zero:
private static int[,] GenerateTT(int size)
{
int[,] table = new int[size,size];
for (int i = 0; i < size; i++)
{
for (int j = 0; j < size; j++)
{
table[i, j] = (i+1) * (j+1);
}
}
return table;
}
The following code sorts rows by the first element using bubble method.
I can't change it to counting sort.
public void SortStack(double[,] n)
{
for (int i = 0; i < n.GetLength(0) - 1; i++)
{
for (int j = i; j < n.GetLength(0); j++)
{
if (n[i, 0] > n[j, 0])
{
for (int k = 0; k < n.GetLength(1); k++)
{
var temp = n[i, k];
n[i, k] = n[j, k];
n[j, k] = temp;
}
}
}
}
}
Please help.
As you do bubble sort based on first element of each row. you should do counting sort like that too. so you just need to count first item of each row.
private static int[,] CountingSort2D(int[,] arr)
{
// find the max number by first item of each row
int max = arr[0, 0];
for (int i = 0; i < arr.GetLength(0); i++)
{
if (arr[i, 0] > max) max = arr[i, 0];
}
// we want to get count of first items of each row. thus we need 1d array.
int[] counts = new int[max + 1];
// do the counting. again on first index of each row
for (int i = 0; i < arr.GetLength(0); i++)
{
counts[arr[i, 0]]++;
}
for (int i = 1; i < counts.Length; i++)
{
counts[i] += counts[i - 1];
}
// result is sorted array
int[,] result = new int[arr.GetLength(0), arr.GetLength(1)];
for (int i = arr.GetLength(0) - 1; i >= 0; i--)
{
counts[arr[i, 0]]--;
// now we need to copy columns too. thus we need another loop
for (int j = 0; j < arr.GetLength(1); j++)
{
result[counts[arr[i, 0]], j] = arr[i, j];
}
}
return result;
}
Here is the test.
static void Main()
{
Random rand = new Random();
int[,] arr = new int[3,3];
for (int i = 0; i < 3; i++)
{
for (int j = 0; j < 3; j++)
{
arr[i, j] = rand.Next(0, 100);
}
}
int[,] newarr = CountingSort2D(arr);
for (int i = 0; i < arr.GetLength(0); i++)
{
Console.Write("{ ");
for (int j = 0; j < arr.GetLength(1); j++)
{
Console.Write(arr[i, j] + " ,");
}
Console.Write("} ,");
}
Console.WriteLine();
for (int i = 0; i < newarr.GetLength(0); i++)
{
Console.Write("{ ");
for (int j = 0; j < newarr.GetLength(1); j++)
{
Console.Write(newarr[i, j] + " ,");
}
Console.Write("} ,");
}
Console.WriteLine();
}
Example Output:
{ 49,66,8 },{ 33,39,64 },{ 65,52,76 } // Original array
{ 33,39,64 },{ 49,66,8 },{ 65,52,76 } // Sorted array
enter code here
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace testing_random
{
class Program
{
static void Main(string[] args)
{
int n = 4;
int[,] a = new int[n,n];//declaring the matrix
Random o = new Random();
a[0,0] = o.Next(n);
for (int i = 1; i < n; i++)//filling the first line
{
int d = 1;
while (d != 0)
{
a[i,0] = o.Next(n);
d = 0;
for (int j = 0; j < i; j++)
if (a[i,0] == a[j,0])
d++;
}
}
for (int i = 1; i < n; i++)//filing the first column
{
int d = 1;
while (d != 0)
{
a[0, i] = o.Next(n);
d = 0;
for (int j = 0; j < i; j++)
if (a[0, i] == a[0, j])
d++;
}
}
for (int k = 1; k < n; k++)//filling the rest of the matrix
for (int i = 1; i < n; i++)
{
int d = 1;
while (d != 0)
{
a[i, k] = o.Next(n);
d = 0;
for (int j = 0; j < i; j++)
if (a[i, k] == a[j, k])
d++;
for (int j = 0; j < k; j++)
if (a[i, k] == a[i, j])
d++;
}
}
for (int i = 0; i < n; i++)
{
for (int j = 0; j < n; j++)
Console.Write("{0} ", a[i, j]);
Console.WriteLine();
}
Console.ReadLine();
}
}
}
The output should be a matrix of 4*4 where each column and each line contains each number once.
The problem is when i run the code, not every time i get an output, i think the problem is not every set of first line and column can give a matrix as required the i get into an unending loop.
what i want to do is limit the running time of the application to 100 ms per example,so if the matrix is not filled,the program restarts
What piece of code am i missing?
replace the while( d != 0 ) with a loop which counts up to a certain very large maximum number of iterations. (Try 1000, 100000, whatever.)
Are you trying to randomly insert numbers between 1-4 in the first line of the array? If so there is a much easier way to do it.
You can generate the 4 numbers to be inserted into the array and then just look through the first line of the array and set each value.
Random rnd = new Random();
var randomNumbers = Enumerable.Range(1, 4).OrderBy(i => rnd.Next()).ToArray();
for (int i = 0; i < n; i++)
{
a[i, 0] = randomNumbers[i];
}
I have a function to calculate the costMatrix like this code below.
public double[,] makeCostMatrixClassic(List<PointD> firstSeq, List<PointD> secondSeq)
{
double[,] costMatrix = new double[firstSeq.Count, secondSeq.Count];
costMatrix[0, 0] = Math.Round(this.getEuclideanDistance(firstSeq[0], secondSeq[0]), 3);
// For D(n,1)
for (int i = 0; i < firstSeq.Count; i++)
{
for (int j = 0; j <= i; j++)
{
costMatrix[i, 0] += Math.Round(this.getEuclideanDistance(firstSeq[j], secondSeq[0]), 3);
}
}
// For D(1,m)
for (int i = 0; i < secondSeq.Count; i++)
{
for (int j = 0; j <= i; j++)
{
costMatrix[0, i] += Math.Round(this.getEuclideanDistance(firstSeq[0], secondSeq[j]), 3);
}
}
// For D(n,m)
for (int i = 1; i < firstSeq.Count; i++)
{
for (int j = 1; j < secondSeq.Count; j++)
{
double min = this.findMin(costMatrix[i - 1, j - 1], costMatrix[i - 1, j], costMatrix[i, j - 1]);
costMatrix[i, j] = min + Math.Round(this.getEuclideanDistance(firstSeq[i], secondSeq[j]), 3);
}
}
return costMatrix;
}
For the 3rd loop (n,m), how could i improve its performance if the "count" of each Sequence is 1 million points.