【数据结构/C++】二分查找

二分查找：根据索引二分，循环查找的条件是左索引小于等于右索引。

二叉树需要判断自身根是否为NULL，并通过改变current的值进行判断。

#include <iostream>
using namespace std;
// 长度为 N 的有序表nums 中查找 target
int BiSearch(int *nums, int N, int target)
{
  int l = 0, r = N - 1;
  while (l <= r)
  {
    int mid = (l + r) / 2;
    if (target == nums[mid])
    {
      return mid;
    }
    if (target < nums[mid])
    {
      r = mid - 1;
    }
    if (target > nums[mid])
    {
      l = mid + 1;
    }
  }
  return -1;
}
// 二叉树
typedef struct TreeNode
{
  int data;
  struct TreeNode *left, *right;
} TreeNode;
TreeNode *SearchTree(TreeNode *root, int target)
{
  if (!root)
  {
    return NULL;
  }
  TreeNode *current = root;
  while (current)
  {
    if (target == current->data)
    {
      return current;
    }
    if (target < current->data)
    {
      current = current->left;
    }
    else
    {
      current = current->right;
    }
  }
  return NULL;
}
int main()
{
  int nums[10] = {1, 3, 5, 7, 9, 11, 13, 15, 17, 19};
  cout << BiSearch(nums, 10, 5) << endl;
  return 0;
}