二分

供暖器

class Solution {
public:
    int findRadius(vector<int>& houses, vector<int>& heaters) {
        //先将供暖器排序，之后为每个屋子找到最近的供暖器
        heaters.push_back(INT_MIN),heaters.push_back(INT_MAX);
        
        sort(heaters.begin(),heaters.end());
        
        int res = 0;
        
        for(int i=0;i<houses.size();i++){
            
            int l=0,r = heaters.size()-1;
            while(l-r){
                int mid = l+r>>1;
                if(heaters[mid]>houses[i]) r = mid;
                else l = mid+1;
            }
            res = max(res,(int)min(heaters[l]-0ll-houses[i],houses[i]-0ll-heaters[l-1]));
        }
        return res;
    }
};

寻找峰值

//如果左边的比右边的值要小的话，那么在右边就会必有一个值是峰值
class Solution {
public:
    int findPeakElement(vector<int>& nums) {
        
        if(nums.size()==1||nums[0]>nums[1]) return 0;
        int l = 1,r = nums.size()-1;
        while(l-r){
            int mid = l+r+1>>1;
            if(nums[mid]>nums[mid-1]) l = mid;
            else r = mid-1;
        }
        return l;
    }
};