package javaLeetCode.primary;

import java.util.Scanner;

public class ImplementStrStr_28 {
    public static void main(String[] args) {
        @SuppressWarnings("resource")
        Scanner input = new Scanner(System.in);
        System.out.println("Please input a string(hayStack):");
        String hayStack = input.next();
        System.out.println("Please input a string(needle):");
        String needle = input.next();
        System.out.println(strStr_1(hayStack, needle));
    }// end main()

    /**
     * 1. Find the same character in "haystack" as the first "needle" character.
     * 2. Start with this character and move back in the "haystack" one by one against the characters in the "needle".
     * */
    /*
     * Input: haystack = "hello", needle = "ll"
     * Output: 2
     * Input: haystack = "helollo", needle = "ll"
     * Output: 4
     * Input: haystack = "aaaaa", needle = "bba"
     *  Output: -1
     *Input: haystack = "a", needle = ""
     * Output: 0
     * Input: haystack = "abcd", needle = "b"
     * Output: 0
     * */
    public static int strStr_1(String hayStack, String needle) {
        int i = 0;
        boolean isInclude = false;
        // Judge "needle" is valid.
        if (needle.length()==0 || needle == null) {
            return 0;
        } // end if
        if (needle.length() > hayStack.length()) {
            return -1;
        } else {
            for (i = 0; i < hayStack.length(); i++) {
                if (hayStack.charAt(i) == needle.charAt(0)&&(hayStack.length()-i>=needle.length())) {
                    int k = i;
                    isInclude = true;
                    for (int j = 1; j < needle.length(); j++) {
                        if (needle.charAt(j) == hayStack.charAt(++k)) {
                            isInclude = true;
                        } else {
                            isInclude = false;
                            break;
                        } // end if
                    } // end for
                } else {
                    continue;
                }//end if
                if (isInclude == true) {
                    break;
                } // end if
            } // end for
        } // end if
        return i < hayStack.length() ? i : -1;
    }// end strStr()

    /**
     * Use the method of  string class.
     * */
    public static int strStr_2(String hayStack, String needle) {
        return hayStack.indexOf(needle);
    }// end strStr()
}//end ImplementStrStr_28