package p;

public class NumberSearch {

/**

* @param args

* 二分查找法

*/

public static void main(String[] args) {

int[] arr = new int[] { 12, 23, 34, 45, 56, 67, 77, 89, 90 };

System.out.println(NumberSearch.NumSearch(arr, 12));

System.out.println(NumSearch(arr, 45));

System.out.println(NumSearch(arr, 67));

System.out.println(NumSearch(arr, 89));

System.out.println(NumSearch(arr, 99));

}

public static int NumSearch(int arr[], int key) {

int start = 0;

int end = arr.length - 1;

while (start <= end) {

int middle = (start + end) / 2;

if (key < arr[middle]) {

end = middle - 1;

} else if (key > arr[middle]) {

start = middle + 1;

} else {

return middle;

}

}

return -1;

}

}