Java使用分治算法实现排序数索引功能示例【二分搜索】

/** * Find the first q and return the index * First method is brutal force * Second may * be Divid and Conquer * * @author open201 * */public class Ono {  /**   * f(n) = s.length = n;   *   * @param s   * @param q   * @return   */  public static int BrutalForceSearch(int[] s, int q) {    for (int i = 0; i < s.length; i++) {      if (q == s[i])        return i;    }    return -1;  }  /**   * f(n) = log(n)   *   * @param s   * @param q   * @return   */  public static int DCSearch(int[] s, int q, int startIndex, int endIndex) {    if (startIndex > endIndex)      return -1;    else {      int mid = (startIndex + endIndex) / 2;      if (s[mid] == q)        return mid;      else {        if (s[mid] > q)          return DCSearch(s, q, startIndex,mid-1);        else          return DCSearch(s, q, mid+ 1,endIndex);      }    }  }  public static void main(String[] args) {    int [] s = new int[10000000];    for(int i = 0;i<10000000;i++){      s[i] = i;    }    int q = 10000000-1;    long startTime = System.currentTimeMillis();    System.out.println(BrutalForceSearch(s, q));    long endTime = System.currentTimeMillis();    System.out.println(endTime-startTime);    startTime = System.currentTimeMillis();    System.out.println(DCSearch(s, q, 0, s.length - 1));    endTime = System.currentTimeMillis();    System.out.println(endTime-startTime);  }}