704. Binary Search

Posted 2021-01-13 real1587

Given a sorted (in ascending order) integer array nums of n elements and a target value, write a function to search target in nums. If targetexists, then return its index, otherwise return -1.

Example 1:

Input: nums = [-1,0,3,5,9,12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4

Example 2:

Input: nums = [-1,0,3,5,9,12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1

 

Note:

1. You may assume that all elements in nums are unique.
2. n will be in the range [1, 10000].
3. The value of each element in nums will be in the range [-9999, 9999].

在有序的数组里面找数字，没有找到则返回-1，二分查找解决。

 1 int search(int* nums, int numsSize, int target) {
 2      int left=0;
 3     int right=numsSize;
 4     int mid;
 5     while(left<right){
 6         mid=left+(right-left)/2;
 7         if(nums[mid]==target){return mid;}
 8         else if(nums[mid]<target){left=mid+1;}
 9         else{right=mid;}
10     }
11     return -1;
12 }