Half Monotonous String - Google Top Interview Questions


Problem Statement :


You are given a lowercase alphabet string s of even length consisting of lowercase alphabet letters. 

Return the minimum number of characters that need to be updated such that one of the following three conditions is true for all 0 ≤ i < n/2 and n/2 ≤ j < n:

s[i] > s[j] or
s[i] < s[j] or
s[i] == s[j]
Constraints

0 ≤ n ≤ 100,000 where n is the length of s

Example 1

Input

s = "aa"

Output

0

Explanation

This string already meets the s[i] == s[j] condition



Example 2

Input

s = "aaabba"

Output

1

Explanation

If we change the last "a" to "b", then we can satisfy the s[i] < s[j] condition.



Example 3

Input

s = "bccbba"

Output

1

Explanation

If we change the first "b" to "c", then we can satisfy the s[i] > s[j] condition.


Solution :



title-img



                        Solution in C++ :

int solve(string s) {
    int len = s.length(), maxCnt = 0;
    vector<int> cnt(26, 0);
    for (int i = 0; i < len; i++) {
        cnt[s[i] - 'a']++;
        maxCnt = max(maxCnt, cnt[s[i] - 'a']);
    }
    int res = len - maxCnt;
    for (char ch = 'b'; ch < 'z'; ch++) {
        int cnt1 = 0, cnt2 = 0, cnt3 = 0, cnt4 = 0;
        for (int i = 0; i < len / 2; i++) {
            if (s[i] >= ch) {
                cnt1++;
            } else if (s[i] <= ch - 1) {
                cnt2++;
            }
        }
        for (int i = len / 2; i < len; i++) {
            if (s[i] >= ch) {
                cnt3++;
            }
            if (s[i] <= ch - 1) {
                cnt4++;
            }
        }
        res = min({res, cnt1 + cnt4, cnt2 + cnt3});
    }
    return res;
}
                    

                        Solution in Java :

import java.util.*;

class Solution {
    public int solve(String s) {
        int N = s.length();
        int[] A = new int[26];
        int[] B = new int[26];
        for (int i = 0; i < N; i++) {
            int c = s.charAt(i) - 'a';
            if (i < N / 2)
                A[c] += 1;
            else
                B[c] += 1;
        }
        int ans = Integer.MAX_VALUE;

        // fix all characters in A to be greater than i and all the characters in B to be less than
        // or equal to i.
        for (int i = 0; i < 26; i++) {
            int fix = 0;
            for (int j = 0; j <= i; j++) fix += A[j];
            for (int j = i + 1; j < 26; j++) fix += B[j];
            ans = Math.min(ans, fix);
        }

        // fix all characters in A to be less than i and all the characters in B to be greater than
        // or equal to i.
        for (int i = 0; i < 26; i++) {
            int fix = 0;
            for (int j = i; j < 26; j++) fix += A[j];
            for (int j = 0; j < i; j++) fix += B[j];
            ans = Math.min(ans, fix);
        }

        // fix all characters in A and B to equal i.
        for (int i = 0; i < 26; i++) {
            int fix = N - (A[i] + B[i]);
            ans = Math.min(ans, fix);
        }

        return ans;
    }
}
                    

                        Solution in Python : 
                            
class Solution:
    def solve(self, s):
        n = len(s)
        left = Counter(s[: n >> 1])
        right = Counter(s[n >> 1 :])

        ans = n
        for pivot in ascii_lowercase:
            # All same
            ans = min(ans, n - left[pivot] - right[pivot])

            # left <= pivot < right
            good = sum(left[c] for c in left if c <= pivot)
            good += sum(right[c] for c in right if c > pivot)
            ans = min(ans, n - good)

            # right <= pivot < left
            good = sum(left[c] for c in left if c > pivot)
            good += sum(right[c] for c in right if c <= pivot)
            ans = min(ans, n - good)

        return ans
                    

View More Similar Problems

Print the Elements of a Linked List

This is an to practice traversing a linked list. Given a pointer to the head node of a linked list, print each node's data element, one per line. If the head pointer is null (indicating the list is empty), there is nothing to print. Function Description: Complete the printLinkedList function in the editor below. printLinkedList has the following parameter(s): 1.SinglyLinkedListNode

View Solution →

Insert a Node at the Tail of a Linked List

You are given the pointer to the head node of a linked list and an integer to add to the list. Create a new node with the given integer. Insert this node at the tail of the linked list and return the head node of the linked list formed after inserting this new node. The given head pointer may be null, meaning that the initial list is empty. Input Format: You have to complete the SinglyLink

View Solution →

Insert a Node at the head of a Linked List

Given a pointer to the head of a linked list, insert a new node before the head. The next value in the new node should point to head and the data value should be replaced with a given value. Return a reference to the new head of the list. The head pointer given may be null meaning that the initial list is empty. Function Description: Complete the function insertNodeAtHead in the editor below

View Solution →

Insert a node at a specific position in a linked list

Given the pointer to the head node of a linked list and an integer to insert at a certain position, create a new node with the given integer as its data attribute, insert this node at the desired position and return the head node. A position of 0 indicates head, a position of 1 indicates one node away from the head and so on. The head pointer given may be null meaning that the initial list is e

View Solution →

Delete a Node

Delete the node at a given position in a linked list and return a reference to the head node. The head is at position 0. The list may be empty after you delete the node. In that case, return a null value. Example: list=0->1->2->3 position=2 After removing the node at position 2, list'= 0->1->-3. Function Description: Complete the deleteNode function in the editor below. deleteNo

View Solution →

Print in Reverse

Given a pointer to the head of a singly-linked list, print each data value from the reversed list. If the given list is empty, do not print anything. Example head* refers to the linked list with data values 1->2->3->Null Print the following: 3 2 1 Function Description: Complete the reversePrint function in the editor below. reversePrint has the following parameters: Sing

View Solution →