二分查找

/**
 * Created by icecookstar on 2015/11/3.
 */
public class BinarySearch {

    private static int binarySearch(int[] matrix, int i, int j, int find) {
        if (i > j) {
            return -1;
        }
        int middle = (i + j) / 2;

        if (matrix[middle] == find) {
            return middle;
        } else if (matrix[middle] < find) {
            return binarySearch(matrix, middle + 1, j, find);
        } else {
            return binarySearch(matrix, i, middle - 1, find);
        }
    }

    private static int binarySearch(int[] matrix, int find) {
        int start = 0;
        int end = matrix.length - 1;
            while (start <= end) {
            int middle = (start + end) / 2;

            if (matrix[middle] == find) {
                return middle;
            } else if (matrix[middle] < find) {
                start = middle + 1;
            } else {
                end = middle - 1;
            }
        }
        return -1;
    }

    public static void main(String[] args) {
        int[] matrix = new int[]{2, 4, 6, 7, 8, 10};
        System.out.print(binarySearch(matrix, 0, matrix.length - 1, 4));
        System.out.print(binarySearch(matrix, 2));
    }
}