找到字符串中最大的字母字符
给定一个字符串，我们的任务是找到最大的字母字符，它的大写和小写都出现在字符串中。应该返回大写字符。如果没有这样的字符，则返回-1，否则打印该字符的大写字母。
示例:
输入: str = "admeDCAB" 输出: D 解释: 字母 D 的大小写字母都存在于字符串中，也是最大的字母字符，因此我们的输出是 D。
输入: str = "dAeB" 输出: -1 解释: 虽然字符串中最大的字符是 d，但大写版本不存在，因此输出为-1。
幼稚方法:为了解决上述问题，幼稚方法是检查字符串中每个字符是否存在大写或小写字符，也就是说对于字母 A，字符串中应该存在“A”和“A”。如果存在这样的字母，那么将跟踪该字符，并且仅当当前字符大于先前选择的字符时才更新。这种方法在最坏的情况下需要 O(n 2 )时间，可以进一步优化。
高效方法:为了优化上述方法，我们使用了英语字母表中有 26 个字符的事实，我们可以通过维护大小为 26 的数组来跟踪小写和大写字符。当遍历给定字符串时，如果当前字符同时以大写和小写字母出现，我们将在两个数组中标记为真。标记了各个数组中的所有字符后，我们将运行一个从 25 到 0 的循环，并检查两个数组中是否都标记了“真”。如果是，那么我们打印该字符的大写字母，否则返回-1。
下面是上述方法的实现:
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to Find the Largest Alphabetic
// Character present in the string of both
// uppercase and lowercase English characters
public class Main {
// Function to find the Largest Alphabetic Character
public static String largestCharacter(String str)
{
// Array for keeping track of both uppercase
// and lowercase english alphabets
boolean[] uppercase = new boolean[26];
boolean[] lowercase = new boolean[26];
char[] arr = str.toCharArray();
for (char c : arr) {
if (Character.isLowerCase(c))
lowercase = true;
if (Character.isUpperCase(c))
uppercase = true;
}
// Iterate from right side of array
// to get the largest index character
for (int i = 25; i >= 0; i--) {
// Check for the character if both its
// uppercase and lowercase exist or not
if (uppercase[i] && lowercase[i])
return (char)(i + 'A') + "";
}
// Return -1 if no such character whose
// uppercase and lowercase present in
// string str
return "-1";
}
// Driver code
public static void main(String[] args)
{
String str = "admeDCAB";
System.out.println(largestCharacter(str));
}
}
Python 3
# Java program to Find the Largest Alphabetic
# Character present in the string of both
# uppercase and lowercase English characters
# Function to find the Largest Alphabetic Character
def largestCharacter(str):
# Array for keeping track of both uppercase
# and lowercase english alphabets
uppercase = [False] * 26
lowercase = [False] * 26
arr = list(str)
for c in arr:
if (c.islower()):
lowercase[ord(c) - ord('a')] = True
if (c.isupper()):
uppercase[ord(c) - ord('A')] = True
# Iterate from right side of array
# to get the largest index character
for i in range(25,-1,-1):
# Check for the character if both its
# uppercase and lowercase exist or not
if (uppercase[i] and lowercase[i]):
return chr(i + ord('A')) + ""
# Return -1 if no such character whose
# uppercase and lowercase present in
# string str
return "-1"
# Driver code
str = "admeDCAB"
print(largestCharacter(str))
# This code is contributed by shivanisinghss2110
C
// C# program to Find the Largest Alphabetic
// char present in the string of both
// uppercase and lowercase English characters
using System;
class GFG{
// Function to find the Largest Alphabetic char
public static String largestchar(String str)
{
// Array for keeping track of both uppercase
// and lowercase english alphabets
bool[] uppercase = new bool[26];
bool[] lowercase = new bool[26];
char[] arr = str.ToCharArray();
foreach(char c in arr)
{
if (char.IsLower(c))
lowercase = true;
if (char.IsUpper(c))
uppercase = true;
}
// Iterate from right side of array
// to get the largest index character
for(int i = 25; i >= 0; i--)
{
// Check for the character if both its
// uppercase and lowercase exist or not
if (uppercase[i] && lowercase[i])
return (char)(i + 'A') + "";
}
// Return -1 if no such character whose
// uppercase and lowercase present in
// string str
return "-1";
}
// Driver code
public static void Main(String[] args)
{
String str = "admeDCAB";
Console.WriteLine(largestchar(str));
}
}
// This code is contributed by amal kumar choubey
java 描述语言
<script>
// JavaScript program to Find the Largest Alphabetic
// Character present in the string of both
// uppercase and lowercase English characters
// Function to find the Largest Alphabetic Character
function largestCharacter(str)
{
// Array for keeping track of both uppercase
// and lowercase english alphabets
let uppercase = new Array(26);
uppercase.fill(false);
let lowercase = new Array(26);
lowercase.fill(false);
let arr = str.split('');
for (let c = 0; c < arr.length; c++) {
if (arr == arr.toLowerCase())
lowercase[arr.charCodeAt() - 97] = true;
if (arr == arr.toUpperCase())
uppercase[arr.charCodeAt() - 65] = true;
}
// Iterate from right side of array
// to get the largest index character
for (let i = 25; i >= 0; i--) {
// Check for the character if both its
// uppercase and lowercase exist or not
if (uppercase[i] && lowercase[i])
return String.fromCharCode(i +
'A'.charCodeAt()) + "";
}
// Return -1 if no such character whose
// uppercase and lowercase present in
// string str
return "-1";
}
let str = "admeDCAB";
document.write(largestCharacter(str));
</script>
输出:
D
时间复杂度: O(n)，其中 n 为字符串长度。 空间复杂度: O(52)
版权属于：月萌API www.moonapi.com，转载请注明出处
