力扣热题 100 —— 搜索插入位置

原题链接

"给定一个排序数组和一个目标值，在数组中找到目标值，并返回其索引。如果目标值不存在于数组中，返回它将会被按顺序插入的位置。" 请必须使用时间复杂度为 O(log n) 的算法。

解题思路

二分查找

取中间值，向两侧迭代

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

func searchInsert(nums []int, target int) int {
    n := len(nums)
    left, right, ans := 0, n - 1, n

    for left <= right {
        mid := (right - left) >> 1 + left
        
        if target <= nums[mid] {
            ans = mid
            right = mid - 1
        } else {
            left = mid + 1
        }
    }
    return ans
}

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

class Solution:
    def searchInsert(self, nums: List[int], target: int) -> int:
        n = len(nums)
        left = 0
        right = n - 1
        ans = n

        while left <= right:
            mid = (right + left) // 2

            if target <= nums[mid]:
                ans = mid
                right = mid - 1
            else:
                left = mid + 1

        return ans

优化一下

直接返回左侧指针替代ans即可

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

func searchInsert(nums []int, target int) int {
    n := len(nums)
    left, right := 0, n - 1

    for left <= right {
        mid := (right - left) >> 1 + left
        
        if target <= nums[mid] {
            ans = mid
            right = mid - 1
        } else {
            left = mid + 1
        }
    }
    return left
}

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

class Solution:
    def searchInsert(self, nums: List[int], target: int) -> int:
        n = len(nums)
        left = 0
        right = n - 1
        ans = n

        while left <= right:
            mid = (right + left) // 2

            if target <= nums[mid]:
                ans = mid
                right = mid - 1
            else:
                left = mid + 1

        return left