编辑代码

public int binarySearch(int array[],int target) {
    int left = 0;
    int right = array.length - 1;   //if array.length = 100,then right = 99
    while(left <= right) {
        int mid = left + (right - left)/2;  //mid = 50
        if(array[mid] == target) {
            return mid;
        }else if(target > array[mid]) {
            left = mid + 1;
        }else {
            right = mid - 1;    
            //assign right a new value again,then the round will recalculate from the madian(mid)
        }
    }
    return -1;
}