Reduce runtime for manipulating string multiple times using Hashmap / other methods












-1














The problem statement is that we have a string and we want to rotate each character to its next character i.e a to b, b to c and z to a. Also, the conversion is based on the number x ( x is <= size of string). The number represents the length of the characters to be converted. Let's say the number is 3 and string is stack which means only first 3 characters need to be converted, so output will be tubck. if the number is 5 then the output will be tubdl.



I am running the solution for 100000000 times and generating the variable number randomly. I have solved this problem using 3 approaches mentioned below:




  1. Convert from character to integer, then increment the integer by 1, then convert the integer back to character.

  2. Using the hashmap to get the updated character value in O(1) time.

  3. Using C, but the approach followed is same as of step # 1


The runtime of the hashmap technique (approach 2) is coming to be more. I don't know why?





Approach #1 is



public static void main(String args) {
Long startTime = System.currentTimeMillis();

String name = "abcdefghijklmnopqrstuvwxyz";
char stringCharArray = name.toCharArray();
Random random = new Random();
for (Integer i = 0; i <100000000; i++) {
{
for (int j = 0; j < random.nextInt(26) + 1; j++) {
if (stringCharArray[j] == 'z') {
stringCharArray[j] = 'a';
} else {
stringCharArray[j] = (char) (((int) (stringCharArray[j])) + 1);
}
}
}
}
Long endtime = System.currentTimeMillis();
System.out.println(endtime-startTime+" ms");

}




Approach # 2 using hashmap is



public static void main(String args) {
HashMap hashMap = new HashMap();
hashMap.put('a', 'b');
hashMap.put('b', 'c');
hashMap.put('c', 'd');
hashMap.put('d', 'e');
hashMap.put('e', 'f');
hashMap.put('f', 'g');
hashMap.put('g', 'h');
hashMap.put('h', 'i');
hashMap.put('i', 'j');
hashMap.put('j', 'k');
hashMap.put('k', 'l');
hashMap.put('l', 'm');
hashMap.put('m', 'n');
hashMap.put('n', 'o');
hashMap.put('o', 'p');
hashMap.put('p', 'q');
hashMap.put('q', 'r');
hashMap.put('r', 's');
hashMap.put('s', 't');
hashMap.put('t', 'u');
hashMap.put('u', 'v');
hashMap.put('v', 'w');
hashMap.put('w', 'x');
hashMap.put('x', 'y');
hashMap.put('y', 'z');
hashMap.put('z', 'a');
Long startTime = System.currentTimeMillis();
String name = "abcdefghijklmnopqrstuvwxyz";
char stringCharArray = name.toCharArray();
Random random = new Random();
for (Integer i = 0; i <100000000; i++) {
{
for (Integer j = 0; j < random.nextInt(26) + 1; j++) {
stringCharArray[j] = (char) hashMap.get(stringCharArray[j]);
}
}
}
Long endtime = System.currentTimeMillis();
System.out.println(endtime-startTime+" ms");
}




Approach #3



#include <stdio.h>
#include <time.h>
#include <zconf.h>
#include <stdlib.h>

int main() {
long start = clock();
char name = "abcdefghijklmnopqrstuvwxyz";
for (int i = 0; i <100000000; i++) {
{
for (int j = 0; j < rand() % 25; j++) {
if (name[j] == 'z') {
name[j] = 'a';
} else {
name[j] = (char) (((int) (name[j])) + 1);
}
}
}
}
long stop = clock();
printf("time taken = %ld sec n",( stop-start)/1000);
}




The runtime of approach 1 is ~ 8150 m, approach 2 is ~ 9700 ms and approach 3 is ~ 5400 ms. I am using MacBook Pro 2.3 GHz Intel Core i5 with 8 GB 2133 MHz LPDDR3.





How do I reduce this runtime, I used stream.parallelize() in java for apprach#2 to make the changes but the runtime was increasing. What am I doing wrong?



The goal is to get the runtime less than approach #3. Is there a way in C to parallelize this and solve in lesser time using pthreads?










share|improve this question









New contributor




Amarjit Singh is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.

























    -1














    The problem statement is that we have a string and we want to rotate each character to its next character i.e a to b, b to c and z to a. Also, the conversion is based on the number x ( x is <= size of string). The number represents the length of the characters to be converted. Let's say the number is 3 and string is stack which means only first 3 characters need to be converted, so output will be tubck. if the number is 5 then the output will be tubdl.



    I am running the solution for 100000000 times and generating the variable number randomly. I have solved this problem using 3 approaches mentioned below:




    1. Convert from character to integer, then increment the integer by 1, then convert the integer back to character.

    2. Using the hashmap to get the updated character value in O(1) time.

    3. Using C, but the approach followed is same as of step # 1


    The runtime of the hashmap technique (approach 2) is coming to be more. I don't know why?





    Approach #1 is



    public static void main(String args) {
    Long startTime = System.currentTimeMillis();

    String name = "abcdefghijklmnopqrstuvwxyz";
    char stringCharArray = name.toCharArray();
    Random random = new Random();
    for (Integer i = 0; i <100000000; i++) {
    {
    for (int j = 0; j < random.nextInt(26) + 1; j++) {
    if (stringCharArray[j] == 'z') {
    stringCharArray[j] = 'a';
    } else {
    stringCharArray[j] = (char) (((int) (stringCharArray[j])) + 1);
    }
    }
    }
    }
    Long endtime = System.currentTimeMillis();
    System.out.println(endtime-startTime+" ms");

    }




    Approach # 2 using hashmap is



    public static void main(String args) {
    HashMap hashMap = new HashMap();
    hashMap.put('a', 'b');
    hashMap.put('b', 'c');
    hashMap.put('c', 'd');
    hashMap.put('d', 'e');
    hashMap.put('e', 'f');
    hashMap.put('f', 'g');
    hashMap.put('g', 'h');
    hashMap.put('h', 'i');
    hashMap.put('i', 'j');
    hashMap.put('j', 'k');
    hashMap.put('k', 'l');
    hashMap.put('l', 'm');
    hashMap.put('m', 'n');
    hashMap.put('n', 'o');
    hashMap.put('o', 'p');
    hashMap.put('p', 'q');
    hashMap.put('q', 'r');
    hashMap.put('r', 's');
    hashMap.put('s', 't');
    hashMap.put('t', 'u');
    hashMap.put('u', 'v');
    hashMap.put('v', 'w');
    hashMap.put('w', 'x');
    hashMap.put('x', 'y');
    hashMap.put('y', 'z');
    hashMap.put('z', 'a');
    Long startTime = System.currentTimeMillis();
    String name = "abcdefghijklmnopqrstuvwxyz";
    char stringCharArray = name.toCharArray();
    Random random = new Random();
    for (Integer i = 0; i <100000000; i++) {
    {
    for (Integer j = 0; j < random.nextInt(26) + 1; j++) {
    stringCharArray[j] = (char) hashMap.get(stringCharArray[j]);
    }
    }
    }
    Long endtime = System.currentTimeMillis();
    System.out.println(endtime-startTime+" ms");
    }




    Approach #3



    #include <stdio.h>
    #include <time.h>
    #include <zconf.h>
    #include <stdlib.h>

    int main() {
    long start = clock();
    char name = "abcdefghijklmnopqrstuvwxyz";
    for (int i = 0; i <100000000; i++) {
    {
    for (int j = 0; j < rand() % 25; j++) {
    if (name[j] == 'z') {
    name[j] = 'a';
    } else {
    name[j] = (char) (((int) (name[j])) + 1);
    }
    }
    }
    }
    long stop = clock();
    printf("time taken = %ld sec n",( stop-start)/1000);
    }




    The runtime of approach 1 is ~ 8150 m, approach 2 is ~ 9700 ms and approach 3 is ~ 5400 ms. I am using MacBook Pro 2.3 GHz Intel Core i5 with 8 GB 2133 MHz LPDDR3.





    How do I reduce this runtime, I used stream.parallelize() in java for apprach#2 to make the changes but the runtime was increasing. What am I doing wrong?



    The goal is to get the runtime less than approach #3. Is there a way in C to parallelize this and solve in lesser time using pthreads?










    share|improve this question









    New contributor




    Amarjit Singh is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.























      -1












      -1








      -1







      The problem statement is that we have a string and we want to rotate each character to its next character i.e a to b, b to c and z to a. Also, the conversion is based on the number x ( x is <= size of string). The number represents the length of the characters to be converted. Let's say the number is 3 and string is stack which means only first 3 characters need to be converted, so output will be tubck. if the number is 5 then the output will be tubdl.



      I am running the solution for 100000000 times and generating the variable number randomly. I have solved this problem using 3 approaches mentioned below:




      1. Convert from character to integer, then increment the integer by 1, then convert the integer back to character.

      2. Using the hashmap to get the updated character value in O(1) time.

      3. Using C, but the approach followed is same as of step # 1


      The runtime of the hashmap technique (approach 2) is coming to be more. I don't know why?





      Approach #1 is



      public static void main(String args) {
      Long startTime = System.currentTimeMillis();

      String name = "abcdefghijklmnopqrstuvwxyz";
      char stringCharArray = name.toCharArray();
      Random random = new Random();
      for (Integer i = 0; i <100000000; i++) {
      {
      for (int j = 0; j < random.nextInt(26) + 1; j++) {
      if (stringCharArray[j] == 'z') {
      stringCharArray[j] = 'a';
      } else {
      stringCharArray[j] = (char) (((int) (stringCharArray[j])) + 1);
      }
      }
      }
      }
      Long endtime = System.currentTimeMillis();
      System.out.println(endtime-startTime+" ms");

      }




      Approach # 2 using hashmap is



      public static void main(String args) {
      HashMap hashMap = new HashMap();
      hashMap.put('a', 'b');
      hashMap.put('b', 'c');
      hashMap.put('c', 'd');
      hashMap.put('d', 'e');
      hashMap.put('e', 'f');
      hashMap.put('f', 'g');
      hashMap.put('g', 'h');
      hashMap.put('h', 'i');
      hashMap.put('i', 'j');
      hashMap.put('j', 'k');
      hashMap.put('k', 'l');
      hashMap.put('l', 'm');
      hashMap.put('m', 'n');
      hashMap.put('n', 'o');
      hashMap.put('o', 'p');
      hashMap.put('p', 'q');
      hashMap.put('q', 'r');
      hashMap.put('r', 's');
      hashMap.put('s', 't');
      hashMap.put('t', 'u');
      hashMap.put('u', 'v');
      hashMap.put('v', 'w');
      hashMap.put('w', 'x');
      hashMap.put('x', 'y');
      hashMap.put('y', 'z');
      hashMap.put('z', 'a');
      Long startTime = System.currentTimeMillis();
      String name = "abcdefghijklmnopqrstuvwxyz";
      char stringCharArray = name.toCharArray();
      Random random = new Random();
      for (Integer i = 0; i <100000000; i++) {
      {
      for (Integer j = 0; j < random.nextInt(26) + 1; j++) {
      stringCharArray[j] = (char) hashMap.get(stringCharArray[j]);
      }
      }
      }
      Long endtime = System.currentTimeMillis();
      System.out.println(endtime-startTime+" ms");
      }




      Approach #3



      #include <stdio.h>
      #include <time.h>
      #include <zconf.h>
      #include <stdlib.h>

      int main() {
      long start = clock();
      char name = "abcdefghijklmnopqrstuvwxyz";
      for (int i = 0; i <100000000; i++) {
      {
      for (int j = 0; j < rand() % 25; j++) {
      if (name[j] == 'z') {
      name[j] = 'a';
      } else {
      name[j] = (char) (((int) (name[j])) + 1);
      }
      }
      }
      }
      long stop = clock();
      printf("time taken = %ld sec n",( stop-start)/1000);
      }




      The runtime of approach 1 is ~ 8150 m, approach 2 is ~ 9700 ms and approach 3 is ~ 5400 ms. I am using MacBook Pro 2.3 GHz Intel Core i5 with 8 GB 2133 MHz LPDDR3.





      How do I reduce this runtime, I used stream.parallelize() in java for apprach#2 to make the changes but the runtime was increasing. What am I doing wrong?



      The goal is to get the runtime less than approach #3. Is there a way in C to parallelize this and solve in lesser time using pthreads?










      share|improve this question









      New contributor




      Amarjit Singh is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      The problem statement is that we have a string and we want to rotate each character to its next character i.e a to b, b to c and z to a. Also, the conversion is based on the number x ( x is <= size of string). The number represents the length of the characters to be converted. Let's say the number is 3 and string is stack which means only first 3 characters need to be converted, so output will be tubck. if the number is 5 then the output will be tubdl.



      I am running the solution for 100000000 times and generating the variable number randomly. I have solved this problem using 3 approaches mentioned below:




      1. Convert from character to integer, then increment the integer by 1, then convert the integer back to character.

      2. Using the hashmap to get the updated character value in O(1) time.

      3. Using C, but the approach followed is same as of step # 1


      The runtime of the hashmap technique (approach 2) is coming to be more. I don't know why?





      Approach #1 is



      public static void main(String args) {
      Long startTime = System.currentTimeMillis();

      String name = "abcdefghijklmnopqrstuvwxyz";
      char stringCharArray = name.toCharArray();
      Random random = new Random();
      for (Integer i = 0; i <100000000; i++) {
      {
      for (int j = 0; j < random.nextInt(26) + 1; j++) {
      if (stringCharArray[j] == 'z') {
      stringCharArray[j] = 'a';
      } else {
      stringCharArray[j] = (char) (((int) (stringCharArray[j])) + 1);
      }
      }
      }
      }
      Long endtime = System.currentTimeMillis();
      System.out.println(endtime-startTime+" ms");

      }




      Approach # 2 using hashmap is



      public static void main(String args) {
      HashMap hashMap = new HashMap();
      hashMap.put('a', 'b');
      hashMap.put('b', 'c');
      hashMap.put('c', 'd');
      hashMap.put('d', 'e');
      hashMap.put('e', 'f');
      hashMap.put('f', 'g');
      hashMap.put('g', 'h');
      hashMap.put('h', 'i');
      hashMap.put('i', 'j');
      hashMap.put('j', 'k');
      hashMap.put('k', 'l');
      hashMap.put('l', 'm');
      hashMap.put('m', 'n');
      hashMap.put('n', 'o');
      hashMap.put('o', 'p');
      hashMap.put('p', 'q');
      hashMap.put('q', 'r');
      hashMap.put('r', 's');
      hashMap.put('s', 't');
      hashMap.put('t', 'u');
      hashMap.put('u', 'v');
      hashMap.put('v', 'w');
      hashMap.put('w', 'x');
      hashMap.put('x', 'y');
      hashMap.put('y', 'z');
      hashMap.put('z', 'a');
      Long startTime = System.currentTimeMillis();
      String name = "abcdefghijklmnopqrstuvwxyz";
      char stringCharArray = name.toCharArray();
      Random random = new Random();
      for (Integer i = 0; i <100000000; i++) {
      {
      for (Integer j = 0; j < random.nextInt(26) + 1; j++) {
      stringCharArray[j] = (char) hashMap.get(stringCharArray[j]);
      }
      }
      }
      Long endtime = System.currentTimeMillis();
      System.out.println(endtime-startTime+" ms");
      }




      Approach #3



      #include <stdio.h>
      #include <time.h>
      #include <zconf.h>
      #include <stdlib.h>

      int main() {
      long start = clock();
      char name = "abcdefghijklmnopqrstuvwxyz";
      for (int i = 0; i <100000000; i++) {
      {
      for (int j = 0; j < rand() % 25; j++) {
      if (name[j] == 'z') {
      name[j] = 'a';
      } else {
      name[j] = (char) (((int) (name[j])) + 1);
      }
      }
      }
      }
      long stop = clock();
      printf("time taken = %ld sec n",( stop-start)/1000);
      }




      The runtime of approach 1 is ~ 8150 m, approach 2 is ~ 9700 ms and approach 3 is ~ 5400 ms. I am using MacBook Pro 2.3 GHz Intel Core i5 with 8 GB 2133 MHz LPDDR3.





      How do I reduce this runtime, I used stream.parallelize() in java for apprach#2 to make the changes but the runtime was increasing. What am I doing wrong?



      The goal is to get the runtime less than approach #3. Is there a way in C to parallelize this and solve in lesser time using pthreads?







      java c++ performance c pthreads






      share|improve this question









      New contributor




      Amarjit Singh is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.











      share|improve this question









      New contributor




      Amarjit Singh is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.









      share|improve this question




      share|improve this question








      edited 11 mins ago





















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      asked 50 mins ago









      Amarjit Singh

      992




      992




      New contributor




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      New contributor





      Amarjit Singh is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






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