二分法查找

二分法查找适合于有序集合或数组

static int HalfSearch(int[] numArr,int num){    //确定查找的范围    int low = 0;    int high = numArr.Length-1;    int mid = 0;    while (low <= high)    {        mid = (low + high) / 2;        if (numArr[mid] == num)        {            return mid;        }        else if (numArr[mid] > num)        {            high = mid - 1;        }        else        {            low = mid + 1;        }    }    return -1;}