二分查找实现代码 注意点：1.循环退出条件low<=high而不是low<high；2.mid的取值，mid = (low + high) / 2;可能溢出，改进方法：mid = low + (high - low) / 2,极致优化，位运算：mid = low + ((high - low) >>1)；3.low和high的更新

BinarySerach.c

int bsearch(int[] a, int n, int value) {
  int low = 0;
  int high = n - 1;
 
  while (low <= high) {
    int mid = low + ((high - low) >>1);
    if (a[mid] == value) {
      return mid;
    } else if (a[mid] < value) {
      low = mid + 1;
    } else {
      high = mid - 1;
    }
  }
 
  return -1;
}