【LeetCode 35】 Search Insert Position

題目描述

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

思路

二分，找第一個 ≥ target 的數字下標。

代碼

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