Related programming problems of string

Number of string occurrences

  character string A, Another string B, Calculation B The string is in A Several times in the string

  Example :  dsabdnabdsnabeabiwpabekabd   **ab**

- Implementation process
  - Index the string to find indexOf
  - Index record of the found string , Intercept the string
  - Until you find the unknown , indexOf The method is -1
  - Once you find , Counter ++

 

 /**
     * @param str   Original string 
     * @param sub   String to find 
     * @return   Number of occurrences 
     */
    public static int stringCount(String str ,String sub){
        // Defining variables , Counter 
        int count = 0;
        // Defining variables , Record the index after string search 
        int index = 0;

        // For the position where the string appears , The query 
        // Search over and over again , Using a loop while
        // The cyclic condition is indexOf Method returns -1
        while ( (index=str.indexOf(sub))  != -1 ) {
            // Cycle executed index !=-1  The string appears 
            count ++;
            // Intercepting string , Start index  index+ The length of the searched string 
            str = str.substring(index + sub.length());
        }

        return count;
    }

  Which character appears most

  requirement : The specified string can be ( A lowercase letter ) Letter abeegewff , Calculate which character appears the most

  The letters in the qualified string can only have 26 individual

> Find out how many times each character appears , Find the maximum

- Implementation process :
  - String to array ( Single character operation )
  - Create a length of 26 Array of , The counter uses
  - Take out the characters in the array , ( character -97) The index of the corresponding array , Counter ++
  - Find the maximum value in the array

  /**
     *  Look up the string , Which character appears the most 
     * @param str   To find a string 
     * @return   Returns the character with the most occurrences 
     */
    public static char charCount(String str){
        // String to array 
        char[] chars = str.toCharArray();
        // Definition 26 An array of lengths , Save the number of occurrences of each character 
        int[] count = new int[26];
        // Traversal array 
        for (int i = 0 ; i < chars.length; i++){
            // Take out a single character 
            char ch = chars[i];
            // character  - 97  Use as an index of an array  ( Array , Counter array )
            count[ ch - 97 ] ++;
        }
        //System.out.println("Arrays.toString(count) = " + Arrays.toString(count));
        // Take out count Array , Index of maximum value 
        int index = 0 ; // Array maximum index 
        int max = count[0];
        for(int i = 1 ; i < count.length ; i++){
            if (max < count[i]){
                index = i;
                max = count[i];
            }
        }
       //index Indexes , Exactly different from the character 97
        return (char) (index+97);
    }