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35. Search Insert Position

Description

Given a sorted array of distinct integers 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 must write an algorithm with O(log n) runtime complexity.

 

Example 1:

Input: nums = [1,3,5,6], target = 5
Output: 2

Example 2:

Input: nums = [1,3,5,6], target = 2
Output: 1

Example 3:

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

 

Constraints:

  • 1 <= nums.length <= 104
  • -104 <= nums[i] <= 104
  • nums contains distinct values sorted in ascending order.
  • -104 <= target <= 104

Solutions

Since the array $nums$ is already sorted, we can use the binary search method to find the insertion position of the target value $target$.

The time complexity is $O(\log n)$, and the space complexity is $O(1)$. Here, $n$ is the length of the array $nums$.

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class Solution:
    def searchInsert(self, nums: List[int], target: int) -> int:
        left, right = 0, len(nums)
        while left < right:
            mid = (left + right) >> 1
            if nums[mid] >= target:
                right = mid
            else:
                left = mid + 1
        return left

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class Solution {
    public int searchInsert(int[] nums, int target) {
        int left = 0, right = nums.length;
        while (left < right) {
            int mid = (left + right) >>> 1;
            if (nums[mid] >= target) {
                right = mid;
            } else {
                left = mid + 1;
            }
        }
        return left;
    }
}

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

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func searchInsert(nums []int, target int) int {
    left, right := 0, len(nums)
    for left < right {
        mid := (left + right) >> 1
        if nums[mid] >= target {
            right = mid
        } else {
            left = mid + 1
        }
    }
    return left
}

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use std::cmp::Ordering;
impl Solution {
    pub fn search_insert(nums: Vec<i32>, target: i32) -> i32 {
        let mut left = 0;
        let mut right = nums.len();
        while left < right {
            let mid = left + (right - left) / 2;
            match nums[mid].cmp(&target) {
                Ordering::Less => {
                    left = mid + 1;
                }
                Ordering::Greater => {
                    right = mid;
                }
                Ordering::Equal => {
                    return mid as i32;
                }
            }
        }
        left as i32
    }
}

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/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number}
 */
var searchInsert = function (nums, target) {
    let left = 0;
    let right = nums.length;
    while (left < right) {
        const mid = (left + right) >> 1;
        if (nums[mid] >= target) {
            right = mid;
        } else {
            left = mid + 1;
        }
    }
    return left;
};

Solution 2: Binary Search (Built-in Function)

We can also directly use the built-in function for binary search.

The time complexity is $O(\log n)$, where $n$ is the length of the array $nums$. The space complexity is $O(1)$.

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class Solution:
    def searchInsert(self, nums: List[int], target: int) -> int:
        return bisect_left(nums, target)

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class Solution {
    public int searchInsert(int[] nums, int target) {
        int i = Arrays.binarySearch(nums, target);
        return i < 0 ? -i - 1 : i;
    }
}

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class Solution {
public:
    int searchInsert(vector<int>& nums, int target) {
        return lower_bound(nums.begin(), nums.end(), target) - nums.begin();
    }
};

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func searchInsert(nums []int, target int) int {
    return sort.SearchInts(nums, target)
}

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class Solution {
    /**
     * @param integer[] $nums
     * @param integer $target
     * @return integer
     */

    function searchInsert($nums, $target) {
        $key = array_search($target, $nums);
        if ($key !== false) {
            return $key;
        }

        $nums[] = $target;
        sort($nums);
        return array_search($target, $nums);
    }
}

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