Find the smallest window in a string containing all characters of another string (With smallest window)

Find the smallest window in a string containing all characters of another string (With smallest window)

Smallest window  

Given two strings string1 and string2, find the smallest substring in string1 containing all characters of string2 efficiently.
For Example:

Steps:

• Generate all substrings which starts with any one character from the pattern string
• Iterate all substrings which we generated and compare each character from the pattern string with the substring and check for all characters present or not
• If all characters present in substring then trim extra characters and choose the smallest window string

Java code:

public class StringInSmallestWindow {

 public static void main(String[] args) {

  String str = "niharika";
  String findStr = "ir";
  String result = null;

  if (str.length() < findStr.length()) {
   System.out.println("Pattern string is greater than source string");
   return;
  }

  int j = 0;
  String[] arr = new String[str.length()];
  // Get all substring which starts with any one character from the
  // pattern string
  for (int i = 0; i < str.length(); i++) {
   if (findStr.contains(str.charAt(i) + "") && str.substring(i).length() >= findStr.length()) {
    arr[j++] = str.substring(i);
   }
  }

  // Iterate all substrings which we generated
  for (int pnt = 0; pnt < j; pnt++) {

   String string = arr[pnt];
   char[] tmp = findStr.toCharArray();

   int cnt = tmp.length;
   int lastIndex = 0;

   // Compare each character from the pattern string with the substring
   // and check for all characters present or not
   for (int i = 0; i < tmp.length; i++) {

    if (string.contains(tmp[i] + "")) {
     if (lastIndex < string.indexOf(tmp[i])) {
      lastIndex = string.indexOf(tmp[i]);
     }
     string = string.substring(0, string.indexOf(tmp[i])) + '\0'
       + string.substring(string.indexOf(tmp[i]) + 1);
     tmp[i] = '\0';
     cnt--;
    }
   }

   // If all characters present in substring then trim extra characters
   // and choose the smallest window string
   if (cnt <= 0) {
    arr[pnt] = arr[pnt].substring(0, lastIndex + 1);
    result = arr[pnt].length() < result.length() ? arr[pnt] : result;
   }

  }
  System.out.println("\nInput String           : " + str);
  System.out.println("\n2nd String to find     : " + findStr);
  System.out.println("\nSmallest window string : " + result);
 }
}

OUTPUT:

Input String           : niharika

2nd String to find     : ir

Smallest window string : ri