Leetcode: 35. Search Insert Position

Description

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.

You may assume no duplicates in the array.

Example

Here are few examples.

[1,3,5,6], 5 → 2
[1,3,5,6], 2 → 1
[1,3,5,6], 7 → 4
[1,3,5,6], 0 → 0

思路

• 思路1, 二分查找
• 思路2，線性
• 線性跑出來比二分快一倍。這測試用例。。

代碼

• 二分

  class Solution {
  public:
  int searchInsert(vector<int>& nums, int target) {
      int len = nums.size();
      if(len == 0) return 0;
  
      int low = 0, high = len - 1, mid = 0;
  
      while(low <= high){
          mid = low + (high - low) / 2;
  
          if(nums[mid] == target) return mid;
          else if(nums[mid] > target) high = mid - 1;
          else low = mid + 1;
      }
  
      return low;
  }
  };

• 線性

  class Solution {
  public:
  int searchInsert(vector<int>& nums, int target) {
      int len = nums.size();
      if(len == 0) return 0;
  
      int i = 0;
      for(i = 0; i < len; ++i){
          if(nums[i] >= target)
              return i;
      }
      return i;
  }
  };