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algorithms

Check if a string is palindrome in C#

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Here we will be checking if a string is palindrome. To check if string is palindrome we need to know the occurrence of each character. Every character should occur even number of times. This is except the case when the length of the string is not even. So for example, if the size of the string is 5 then except one all other characters should occur even number of times.

Check if a string is palindrome in csharp


using System;
using System.Collections.Generic;
namespace CSharpAlgos
{
class Program
{
static void Main(string[] args)
{
string name="abczcba";
bool pal=true;
//if the string contains even characters
if(name.Length%2==0)
{
//each character should occur even number of times
Dictionary<char,int> dic=newDictionary<char, int>();
foreach(var ch inname)
{
if(!dic.ContainsKey(ch))
dic.Add(ch,0);
dic[ch]=dic[ch]+1;}
foreach(KeyValuePair<char,int> kv indic)
{
if(kv.Value%2!=0)
pal=false;
Console.Write(kv.Value);
}}
else
{
int count=0;
//each character should occur even number of times
Dictionary<char,int> dic=newDictionary<char, int>();
foreach(var ch inname)
{
if(!dic.ContainsKey(ch))
dic.Add(ch,0);
dic[ch]=dic[ch]+1;}
foreach(KeyValuePair<char,int> kv indic)
{
if(kv.Value%2!=0)
{
count++;
if(count==2)
pal=false;
}
Console.Write(kv.Value);
}
}
Console.WriteLine(pal);
}
}
}

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Binary Search in C#

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Binary Search is one of the methods of searching an item in a list of items.Here we will look into how to implement binary search in C#.

We first need to calculate the middle element in the list and then compare the element we are searching with this middle element.

To calculate middle element we use the formula:

middle element = highest element + lowest element  / 2

After we calculate the middle element we compare the element we are searching for with this element.There can be three conditions:

  • if  value is equal to the middle element
  • if  value is less than the middle element
  • if  value is greater than the middle element


class BinarySearch
{
public static int Find(int[] numList, int val)
{

int low = 0;
int high = numList.Length-1;
int mid = 0;
while (low < =high)
{
Console.WriteLine(string.Format("low=0,high={1}",low,high));
mid = high +low/ 2;

if (val == numList[mid])
{
Console.WriteLine(string.Format("found value"));
return mid;
}
if (val > numList[mid])
{
Console.WriteLine(string.Format("value is less than the middle element"));
low = mid + 1;

Console.WriteLine(string.Format("low=0,high={1},mid={2}", low, high, mid));
}
else
{
Console.WriteLine(string.Format("value is greater than the middle element"));
high = mid - 1;
}

}

return -1;

}
}

 

 

public static void Main()
{
var location = BinarySearch.Find(new int[] { 1, 2, 3, 4,5,6,7,8,9 }, 6);
Console.WriteLine(location);

}

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