35. Search Insert Position(二分查找)

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 1:

Input: [1,3,5,6], 5
Output: 2

Example 2:

Input: [1,3,5,6], 2
Output: 1

Example 3:

Input: [1,3,5,6], 7
Output: 4

Example 4:

Input: [1,3,5,6], 0
Output: 0

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

　　

 class Solution {
     public int searchInsert(int[] nums, int target) {
         int n = nums.length;
         int lo = 0;
         int hi = n-1;
         while(lo<=hi){
             int mid = lo+(hi-lo)/2;
             if(nums[mid]>target)
                 hi = mid - 1;
             else if (nums[mid]<target)
                 lo = mid + 1;
             else
                 return mid;
         }
         return lo;
     }
 }