35. Search Insert Position

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

二分搜索法

c++11

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

重新写了一遍，差不多

class Solution {
public:
    int searchInsert(vector<int>& nums, int target) {
        if (target > nums.back()) return nums.size();
        if (target < nums.front()) return 0;

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