二分查找

//递归版二分查找
int binarySearch(vector<int>& nums,int left,int right,int target){
    if(nums.empty()) return -1;
    int mid=0;
    while(left<right){
        mid=(left+right)/2;
        if(nums[mid]==target)
        return mid;
        else if(nums[mid]>target)
        return binarySearch(nums,left,mid,target);
        else
        return binarySearch(nums,mid+1,right,target);
    }
    return -1;
}
//非递归版二分查找
int binarySearch(vector<int>& nums,int left,int right,int target){
    if(nums.empty()) return -1;
    int mid=0;
    while(left<right){
        mid=(left+right)/2;
        if(nums[mid]==target)
        return mid;
        else if(nums[mid]>target)
        right=mid;
        else
        left=mid+1;
    }
    return -1;
}
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