Leetcode-35. Search Insert Position

题目：

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.

Here are few examples.

[1,3,5,6], 5 → 2

[1,3,5,6], 2 → 1

[1,3,5,6], 7 → 4

[1,3,5,6], 0 → 0

给定一个有序的无元素重复的数组，寻找目标，如果找到，返回位置，否则返回插入位置，使插入后数组仍有序。

思路

二分查找即可，每次取中间，如果等于目标即返回，否则根据大小关系切去一半，时间复杂度为O(logn)，空间复杂度为O(1)。

代码

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