URLify 给定的字符串（用 %20 替换空格）
编写一个方法，用 '%20' 替换字符串中的所有空格。您可以假设字符串有足够的空间来容纳额外的字符，并且您得到了字符串的“真实”长度。
例子：
Input: "Mr John Smith", 13
Output: Mr%20John%20Smith
Input: "Mr John Smith ", 13
Output: Mr%20John%20Smith一个简单的解决方案是创建一个辅助字符串并一个一个地复制字符。每当遇到空格时，用 %20 代替它。
假设我们在输入字符串中有额外的空间，则可以更好地就地执行。我们首先计算输入字符串中的空格数。使用这个计数，我们可以找到修改（或结果）字符串的长度。在计算新长度后，我们从末尾就地填充字符串。
下面是上述方法的实现：
C++
// C++ program to replace spaces with %20
#include
// Maximum length of string after modifications.
const int MAX = 1000;
// Replaces spaces with %20 in-place and returns
// new length of modified string. It returns -1
// if modified string cannot be stored in str[]
int replaceSpaces(char str[])
{
// count spaces and find current length
int space_count = 0, i;
for (i = 0; str[i]; i++)
if (str[i] == ' ')
space_count++;
// Remove trailing spaces
while (str[i-1] == ' ')
{
space_count--;
i--;
}
// Find new length.
int new_length = i + space_count * 2 + 1;
// New length must be smaller than length
// of string provided.
if (new_length > MAX)
return -1;
// Start filling character from end
int index = new_length - 1;
// Fill string termination.
str[index--] = '\0';
// Fill rest of the string from end
for (int j=i-1; j>=0; j--)
{
// inserts %20 in place of space
if (str[j] == ' ')
{
str[index] = '0';
str[index - 1] = '2';
str[index - 2] = '%';
index = index - 3;
}
else
{
str[index] = str[j];
index--;
}
}
return new_length;
}
// Driver code
int main()
{
char str[MAX] = "Mr John Smith ";
// Prints the replaced string
int new_length = replaceSpaces(str);
for (int i=0; i Java
// Java program to replace spaces with %20
class GFG
{
// Maximum length of string
// after modifications.
static int MAX = 1000;
// Replaces spaces with %20 in-place
// and returns new length of modified string.
// It returns -1 if modified string
// cannot be stored in str[]
static char[] replaceSpaces(char[] str)
{
// count spaces and find current length
int space_count = 0, i = 0;
for (i = 0; i < str.length; i++)
if (str[i] == ' ')
space_count++;
// count spaces and find current length
while (str[i - 1] == ' ')
{
space_count--;
i--;
}
// Find new length.
int new_length = i + space_count * 2;
// New length must be smaller than length
// of string provided.
if (new_length > MAX)
return str;
// Start filling character from end
int index = new_length - 1;
char[] old_str = str;
str = new char[new_length];
// Fill rest of the string from end
for (int j = i - 1; j >= 0; j--)
{
// inserts %20 in place of space
if (old_str[j] == ' ')
{
str[index] = '0';
str[index - 1] = '2';
str[index - 2] = '%';
index = index - 3;
}
else
{
str[index] = old_str[j];
index--;
}
}
return str;
}
// Driver Code
public static void main(String[] args)
{
char[] str = "Mr John Smith ".toCharArray();
// Prints the replaced string
str = replaceSpaces(str);
for (int i = 0; i < str.length; i++)
System.out.print(str[i]);
}
}
// This code is contributed by
// sanjeev2552Python3
# Maximum length of string after modifications.
MAX = 1000;
# Replaces spaces with %20 in-place and returns
# new length of modified string. It returns -1
# if modified string cannot be stored in str[]
def replaceSpaces(string):
# Remove remove leading and trailing spaces
string = string.strip()
i = len(string)
# count spaces and find current length
space_count = string.count(' ')
# Find new length.
new_length = i + space_count * 2
# New length must be smaller than length
# of string provided.
if new_length > MAX:
return -1
# Start filling character from end
index = new_length - 1
string = list(string)
# Fill string array
for f in range(i - 2, new_length - 2):
string.append('0')
# Fill rest of the string from end
for j in range(i - 1, 0, -1):
# inserts %20 in place of space
if string[j] == ' ':
string[index] = '0'
string[index - 1] = '2'
string[index - 2] = '%'
index = index - 3
else:
string[index] = string[j]
index -= 1
return ''.join(string)
# Driver Code
if __name__ == '__main__':
s = "Mr John Smith "
s = replaceSpaces(s)
print(s)
# This code is contributed by VinayakC#
// C# program to replace spaces with %20
using System;
class GFG
{
// Maximum length of string
// after modifications.
static int MAX = 1000;
// Replaces spaces with %20 in-place
// and returns new length of modified string.
// It returns -1 if modified string
// cannot be stored in []str
static char[] replaceSpaces(char[] str)
{
// count spaces and find current length
int space_count = 0, i = 0;
for (i = 0; i < str.Length; i++)
if (str[i] == ' ')
space_count++;
// count spaces and find current length
while (str[i - 1] == ' ')
{
space_count--;
i--;
}
// Find new length.
int new_length = i + space_count * 2;
// New length must be smaller than
// length of string provided.
if (new_length > MAX)
return str;
// Start filling character from end
int index = new_length - 1;
char[] new_str = str;
str = new char[new_length];
// Fill rest of the string from end
for (int j = i - 1; j >= 0; j--)
{
// inserts %20 in place of space
if (new_str[j] == ' ')
{
str[index] = '0';
str[index - 1] = '2';
str[index - 2] = '%';
index = index - 3;
}
else
{
str[index] = new_str[j];
index--;
}
}
return str;
}
// Driver Code
public static void Main(String[] args)
{
char[] str = "Mr John Smith ".ToCharArray();
// Prints the replaced string
str = replaceSpaces(str);
for (int i = 0; i < str.Length; i++)
Console.Write(str[i]);
}
}
// This code is contributed by 29AjayKumarJava
// Java implementation of above approach
class GFG
{
public static void main(String[] args)
{
// Instantiate the string
String str = "Mr John Smith ";
// Trim the given string
str = str.trim();
// Replace All space (unicode is \\s) to %20
str = str.replaceAll("\\s", "%20");
// Display the result
System.out.println(str);
}
}Python3
# Python3 implementation of above approach
# Instantiate the string
s = "Mr John Smith "
# Trim the given string
s = s.strip()
# Replace All space (unicode is \\s) to %20
s = s.replace(' ', "%20")
# Display the result
print(s)
# This code is contributed by vinayakC#
// C# implementation of above approach
using System;
class GFG
{
public static void Main()
{
// Instantiate the string
String str = "Mr John Smith ";
// Trim the given string
str = str.Trim();
// Replace All space (unicode is \\s) to %20
str = str.Replace(" ", "%20");
// Display the result
Console.Write(str);
}
}
// This code is contributed by Rajput-JiJavascript
C++
#include
using namespace std;
void replaceSpaces(string input)
{
string rep = "%20";
for(int i=0 ; i 输出：
Mr%20John%20Smith时间复杂度： O(n)，其中 n 是字符串的真实长度。
辅助空间： O(1)，因为上面的程序是就地算法。
方法二：
修剪字符串并调用 replaceAll() 方法，将所有空格 Unicode 替换为 %20。
下面是上述方法的实现：
Java
// Java implementation of above approach
class GFG
{
public static void main(String[] args)
{
// Instantiate the string
String str = "Mr John Smith ";
// Trim the given string
str = str.trim();
// Replace All space (unicode is \\s) to %20
str = str.replaceAll("\\s", "%20");
// Display the result
System.out.println(str);
}
}
Python3
# Python3 implementation of above approach
# Instantiate the string
s = "Mr John Smith "
# Trim the given string
s = s.strip()
# Replace All space (unicode is \\s) to %20
s = s.replace(' ', "%20")
# Display the result
print(s)
# This code is contributed by vinayak
C＃
// C# implementation of above approach
using System;
class GFG
{
public static void Main()
{
// Instantiate the string
String str = "Mr John Smith ";
// Trim the given string
str = str.Trim();
// Replace All space (unicode is \\s) to %20
str = str.Replace(" ", "%20");
// Display the result
Console.Write(str);
}
}
// This code is contributed by Rajput-Ji
Javascript
输出：
Mr%20John%20Smith方法 3：使用字符串.replace()函数：
下面是上述方法的实现：
C++
#include
using namespace std;
void replaceSpaces(string input)
{
string rep = "%20";
for(int i=0 ; i 输出：
Mr%20John%20Smith