2020-11-25-35.md

35. 搜索插入位置

https://leetcode-cn.com/problems/search-insert-position/

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。

你可以假设数组中无重复元素。 看到是排序的数组 那么就可以想到是二分法了。

先写一个我最先想到的办法 时间空间是O(N)

var searchInsert = function(nums, target) {
    for(let i = 0;i<nums.length;i++) {
        if(nums[i] >= target) return i
    }
    return nums.length
};

二分法

var searchInsert = function (nums, target) {
    let left = 0
    let right = nums.length
    while (left <= right) {
        let mid = Math.floor(left + (right - left) / 2)
        if (nums[mid] === target) return mid
        if (nums[mid] < target) {
            left = mid + 1
        } else {
            right = mid - 1
        }
    }
    return left
};

JAVA:

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

GO:

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