二分查找法[cpp] view plaincopyint binSearch(int key,int length, int array[])  {          int mid=0;          int start = 0;          int end = length - 1;          while (start <= end) {                mid = (end - start) / 2 + start;                if (key == array[mid]) {                       return mid;                }                if (key < array[mid]) {                       end = mid - 1;                 } else if (key > array[mid]) {                       start = mid + 1;                 } else {                       return mid;                 }          }          return -1;  }