检查给定的字符串是否线性

给定字符串str ，任务是检查给定的字符串是否线性。如果是线性的，则打印“是”，否则打印“否” 。

Let the string be “abcdefghij”. It can be broken as: 
“a” 
“bc” 
“def” 
“ghij” 
if the character a, b, c, and are equal then the given string is linear otherwise not. 
Therefore if the string is of the form “xxaxabcxabcdxabcdexab…” then it is called as the linear string. 
 

例子：

Input: str = “aapaxyayziabcde” 
Output: Yes 
Explanation: 
a 
ap 
axy 
ayzi 
abcde 
All the broken string have same character as the first character.
Input: str = “bbobfycd” 
Output: No 
Explanation: 
b 
bo 
bfy 
cd 
Here b=b=b!=c 
 

办法：检查是否给定的字符串的形式为“xxaxabcxabcdxabcdexab ……”那么，我们要检查，如果在索引0，1，3，6，10个字符，…是平等与否。
如果上述索引处的所有字符均相等，则给定的字符串为线性字符串，否则为线性字符串。
下面是上述方法的实现：

C++

// C++ program for the above approach
#include 
using namespace std;
  
// Function to check if the given
// string is linear or not
int is_linear(string s)
{
    int tmp = 0;
  
    char first = s[0];
  
    // Iterate over string
    for (int pos = 0; pos < s.length();
        pos += tmp) {
  
        // If character is not same as
        // the first character then
        // return false
        if (s[pos] != first) {
            return false;
        }
  
        // Increment the tmp
        tmp++;
    }
  
    return true;
}
  
// Driver Code
int main()
{
    // Given String str
    string str = "aapaxyayziabcde";
  
    // Function Call
    if (is_linear(str)) {
        cout << "Yes" << endl;
    }
    else {
        cout << "No" << endl;
    }
  
    return 0;
}

Java

// Java program for the above approach
import java.util.*;
    
class GFG{
   
// Function to check if the given
// string is linear or not
static boolean is_linear(String s)
{
    int tmp = 0;
    char first = s.charAt(0);
   
    // Iterate over string
    for(int pos = 0; pos < s.length(); 
            pos += tmp)
    {
          
        // If character is not same as
        // the first character then
        // return false
        if (s.charAt(pos) != first)
        {
            return false;
        }
          
        // Increment the tmp
        tmp++;
    }
    return true;
}
  
// Driver code
public static void main(String[] args)
{
      
    // Given String str
    String str = "aapaxyayziabcde";
  
    // Function call
    if (is_linear(str)) 
    {
        System.out.println("Yes");
    }
    else
    {
        System.out.println("No");
    }
}
}
  
// This code is contributed by offbeat

Python3

# Python3 program for the above approach
  
# Function to check if the given
# is linear or not
def is_linear(s):
  
    tmp = 0
    first = s[0]
    pos = 0
      
    # Iterate over string
    while pos < len(s):
  
        # If character is not same as
        # the first character then
        # return false
        if (s[pos] != first):
            return False
          
        # Increment the tmp
        tmp += 1
        pos += tmp
          
    return True
  
# Driver Code
if __name__ == '__main__':
  
    # Given String str
    str = "aapaxyayziabcde"
  
    # Function call
    if (is_linear(str)):
        print("Yes")
    else:
        print("No")
  
# This code is contributed by mohit kumar 29

C#

// C# program for the above approach 
using System;
   
class GFG{
      
// Function to check if the given
// string is linear or not
static bool is_linear(String s)
{
    int tmp = 0;
    char first = s[0];
  
    // Iterate over string
    for(int pos = 0; pos < s.Length;
            pos += tmp)
    {
          
        // If character is not same as
        // the first character then
        // return false
        if (s[pos] != first)
        {
            return false;
        }
  
        // Increment the tmp
        tmp++;
    }
    return true;
}
  
// Driver code
public static void Main(String[] args)
{
      
    // Given String str
    String str = "aapaxyayziabcde";
  
    // Function call
    if (is_linear(str)) 
    {
        Console.Write("Yes");
    }
    else 
    {
        Console.Write("No");
    }
}
}
  
// This code is contributed by grand_master

输出：

Yes

时间复杂度： O(log N)
辅助空间： O(1)