bsearch的溢出问题

在java中为了避免 low+high溢出，可以用无符号右移：正数高位补0，负数高位补1

int mid = (low + high) >>> 1;

如果是在c++中，那么需要先转换为unsigned的再移位

int a=100;
int b;
b=((unsigned int)a)>>1;

或者 int mid = low + ((high - low) / 2);

public static int binarySearch(int[] a, int target) {
 int low = 0;
 int high = a.length - 1;
   while (low <= high) {
     int mid = (low + high) >>> 1;
     int midVal = a[mid];
     if (midVal < target)
         low = mid + 1;
     else if (midVal > target)
         high = mid - 1;
     else
         return mid;
   }
   return -1;
 }