34. Search for a Range

二分法:

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

摘自别人的解法：

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