Given a string S consisting of uppercase and lowercase letters, the task is to check if uppercase characters are used correctly in the given string or not. Correct usage of uppercase characters are as follows:
- All characters in the string are in uppercase. For example, “GEEKS”.
- None of the characters are in uppercase. For example, “neveropen”.
- Only the first character is in uppercase. For example, “Geeks”.
Examples:
Input: S = “Geeks”
Output: Yes
Explanation: Only the first character of the string is in uppercase and all the remaining characters are in lowercase.Input: S = “GeeksForGeeks”
Output: No
Approach: The given problem has already been discussed in Set 1 of this article. This article suggests a different and easy to implement approach which is based on the following two observations:
- If the current letter is a capital alphabet and the previous letter was a small alphabet, return false.
- If the current letter is a small alphabet and the previous letter is a capital alphabet and the previous letter is not the 1st character of the string, return false.
If the complete string has been traversed without violating any of the above two cases, return true.
Below is the implementation of the above approach
C++
// C++ program for the above approach#include <bits/stdc++.h>using namespace std;// Function to check if uppercase// characters are used correctly or notbool detectUppercaseUse(string word){ // Loop to iterate through // the given string S for (int i = 1; i < word.length(); i++) { // Current character is // Capital and previous // character is small if (word[i] - 'A' < 32 && word[i - 1] - 'A' >= 32) { return false; } // Current character is // small and previous is // a capital character else if (word[i] - 'A' >= 32 && word[i - 1] - 'A' < 32) { // If previous char // is the 1st char if (i - 1 == 0) continue; return false; } } // Return true return true;}// Driver Codeint main(){ string S = "GeeKs"; cout << (detectUppercaseUse(S) ? "Yes" : "No"); return 0;} |
Java
// Java program for the above approachimport java.util.*;class GFG{ // Function to check if uppercase // characters are used correctly or not static boolean detectUppercaseUse(char []word) { // Loop to iterate through // the given String S for (int i = 1; i < word.length; i++) { // Current character is // Capital and previous // character is small if (word[i] - 'A' < 32 && word[i - 1] - 'A' >= 32) { return false; } // Current character is // small and previous is // a capital character else if (word[i] - 'A' >= 32 && word[i - 1] - 'A' < 32) { // If previous char // is the 1st char if (i - 1 == 0) continue; return false; } } // Return true return true; } // Driver Code public static void main(String[] args) { String S = "GeeKs"; System.out.print(detectUppercaseUse(S.toCharArray()) ? "Yes" : "No"); }}// This code is contributed by 29AjayKumar |
Python3
# Python code for the above approach # Function to check if uppercase# characters are used correctly or notdef detectUppercaseUse(word): # Loop to iterate through # the given string S for i in range(1, len(word)): # Current character is # Capital and previous # character is small if (ord(word[i]) - ord('A') < 32 and ord(word[i - 1]) - ord('A') >= 32): return False; # Current character is # small and previous is # a capital character elif (ord(word[i]) - ord('A') >= 32 and ord(word[i - 1]) - ord('A') < 32): # If previous char # is the 1st char if (i - 1 == 0): continue; return False; # Return true return True;# Driver CodeS = "GeeKs";print("Yes" if detectUppercaseUse(S) else "No");# This code is contributed by Saurabh Jaiswal |
C#
// C# program for the above approachusing System;class GFG{ // Function to check if uppercase // characters are used correctly or not static bool detectUppercaseUse(string word) { // Loop to iterate through // the given string S for (int i = 1; i < word.Length; i++) { // Current character is // Capital and previous // character is small if (word[i] - 'A' < 32 && word[i - 1] - 'A' >= 32) { return false; } // Current character is // small and previous is // a capital character else if (word[i] - 'A' >= 32 && word[i - 1] - 'A' < 32) { // If previous char // is the 1st char if (i - 1 == 0) continue; return false; } } // Return true return true; } // Driver Code public static void Main() { string S = "GeeKs"; Console.Write((detectUppercaseUse(S) ? "Yes" : "No")); }}// This code is contributed by Samim Hossain Mondal. |
Javascript
<script> // JavaScript code for the above approach // Function to check if uppercase // characters are used correctly or not function detectUppercaseUse(word) { // Loop to iterate through // the given string S for (let i = 1; i < word.length; i++) { // Current character is // Capital and previous // character is small if (word[i].charCodeAt(0) - 'A'.charCodeAt(0) < 32 && word[i - 1].charCodeAt(0) - 'A'.charCodeAt(0) >= 32) { return false; } // Current character is // small and previous is // a capital character else if (word[i].charCodeAt(0) - 'A'.charCodeAt(0) >= 32 && word[i - 1].charCodeAt(0) - 'A'.charCodeAt(0) < 32) { // If previous char // is the 1st char if (i - 1 == 0) continue; return false; } } // Return true return true; } // Driver Code let S = "GeeKs"; document.write(detectUppercaseUse(S) ? "Yes" : "No"); // This code is contributed by Potta Lokesh</script> |
Output
No
Time Complexity: O(N)
Auxiliary Space: O(1)
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