Hexadecimal to Decimal Using Recursion C++

Problem Statment: Write a (regular or tail) recursive function that converts a valid hexadecimal string into a decimal value no longer than 64 bits.

"0x0" => 0
"0x1" => 1
"0xABCD" => 43981

int charTodec(char const ch){

  if(ch>='a'&& ch<='f')
    return ch-'a'+10;
  if(ch>='A'&& ch<='F')
    return ch-'A'+10;
  else
  return ch -'0';
}

unsigned long long int hexTodec(char const* str, unsigned long long result){

  if(*str == '\0')
    return result;
  else{
    result=result*16+charTodec(*str);
    return hexTodec(str+1,result);
  }
}

Comments

Non-decreasing Array - LeetCode

Given an array with n integers, your task is to check if it could become non-decreasing by modifying at most 1 element.We define an array is non-decreasing if array[i] <= array[i + 1] holds for every i (1 <= i < n). Example 1: Input: [4,2,3] Output: True Explanation: You could modify the first 4 to 1 to get a non-decreasing array. Example 2: Input: [4,2,1] Output: False Explanation: You can't get a non-decreasing array by modify at most one element. Note: The n belongs to [1, 10,000]. Source: LeetCode At first glance, it looks like an easy and straightforward problem, but believe me it's greedy problem. In the problem, you are allowed to make atmost "one" modification to make a non-decreasing array. Nondecreasing means that every element is greater than or equal to the one before it e.g. [1,3,4,4,5,6,9]. For example, [2,2,3,2,4] can this become non-decreasing? Yes, by replacing 3 with 2 =>[2,2,2,2,4]. What about this:...

RLE Encoding and Decoding in C++

Given an input string, write a regular recursive function that returns the decoded (uncompresseed form) Run Length Encoded (is a simple form of data compression where repeated character are replaced by count followed by the character repeated) string for the input string. Below are some examples: decode("*") =>* decode("3+") =>+++ decode("11*") =>*********** decode("101+") =>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ decode("abcde10+10*10+10x") =>abcde++++++++++**********++++++++++xxxxxxxxxx decode("\\") =>\ decode("\1\2\3") =>123 decode("13\7x") =>7777777777777x decode("5\\") =>\\\\\ decode("4\12\23\3") =>111122333 decode("4\\2\3") =>\\\\33 NOTE: To represent a single backslash, it’s necessary to place double backslashes (\\) in the input string to obtain the desired in...

Merge Two Binary Trees

Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are not.You need to merge them into a new binary tree. The merge rule is that if two nodes overlap, then sum node values up as the new value of the merged node. Otherwise, the NOT null node will be used as the node of new tree. Example 1: Input: Tree 1 Tree 2 1 2 / \ / \ 3 2 1 3 / \ \ 5 4 7 Output: Merged tree: 3 / \ 4 5 / \ \ 5 4 7 Note: The merging process must start from the root nodes of both trees. Source: LeetCode Solution: We traverse both trees in a p...

{ Programming }

Search This Blog