二分查找——三种模板（C++版本）

模板一：

int binarySearch(vector<int>& nums, int target){
  if(nums.size() == 0)
    return -1;

  int left = 0, right = nums.size() - 1;
  while(left <= right){
    // Prevent (left + right) overflow
    int mid = left + (right - left) / 2;
    if(nums[mid] == target){ return mid; }
    else if(nums[mid] < target) { left = mid + 1; }
    else { right = mid - 1; }
  }

  // End Condition: left > right
  return -1;
}

模板二：

int binarySearch(vector<int>& nums, int target){
  if(nums.size() == 0)
    return -1;

  int left = 0, right = nums.size();
  while(left < right){
    // Prevent (left + right) overflow
    int mid = left + (right - left) / 2;
    if(nums[mid] == target){ return mid; }
    else if(nums[mid] < target) { left = mid + 1; }
    else { right = mid; }
  }

  // Post-processing:
  // End Condition: left == right
  if(left != nums.size() && nums[left] == target) return left;
  return -1;
}

模板三：

int binarySearch(vector<int>& nums, int target){
    if (nums.size() == 0)
        return -1;

    int left = 0, right = nums.size() - 1;
    while (left + 1 < right){
        // Prevent (left + right) overflow
        int mid = left + (right - left) / 2;
        if (nums[mid] == target) {
            return mid;
        } else if (nums[mid] < target) {
            left = mid;
        } else {
            right = mid;
        }
    }

    // Post-processing:
    // End Condition: left + 1 == right
    if(nums[left] == target) return left;
    if(nums[right] == target) return right;
    return -1;
}

 

来源：https://blog.csdn.net/qq_34732729/article/details/100666158