Leetcode:475. Heaters(二分binary search利用)

タイトル:Winter is coming!Your first job during the contest is to design a standard heater with fixed warm radius to warm all the houses.
Now, you are given positions of houses and heaters on a horizontal line, find out minimum radius of heaters so that all houses could be covered by those heaters.
So, your input will be the positions of houses and heaters seperately, and your expected output will be the minimum radius standard of heaters.
Note: Numbers of houses and heaters you are given are non-negative and will not exceed 25000. Positions of houses and heaters you are given are non-negative and will not exceed 10^9. As long as a house is in the heaters’ warm radius range, it can be warmed. All the heaters follow your radius standard and the warm radius will the same.

Example 1:
Input: [1,2,3],[2]
Output: 1
Explanation: The only heater was placed in the position 2, and if we use the radius 1 standard, then all the houses can be warmed.
Example 2:
Input: [1,2,3,4],[1,4]
Output: 1
Explanation: The two heater was placed in the position 1 and 4. We need to use radius 1 standard, then all the

まず暖房器具の配列を並べ替えて、すべてのhouseを遍歴して、各houseに対して、暖房器具の配列の中でbinary searchを行って、命中するならば、暖房器具の位置とhouseの位置が重なって、このhouseの最小半径は0です;ヒットしなかった場合は、返されたindexを使用して、indexの左側と右側の暖房器具座標とhouse座標の差を求め、このhouseの最小半径を見つけます.はっきり言って、ハウスの最近の左右の暖房器具を探しています.コードは次のとおりです.

public static int findRadius(int[] houses, int[] heaters) {
        Arrays.sort(heaters);  
        int result = 0;  
        for(int house:houses) {  
            int index = Arrays.binarySearch(heaters, house);  
            if(index<0) { //index<0,    headers    house,   (-(   ) - 1),                
                index = ~index;  
                int dist1 = index - 1 >= 0 ? house - heaters[index - 1] : Integer.MAX_VALUE;  
                int dist2 = index < heaters.length ? heaters[index] - house : Integer.MAX_VALUE;  

                result = Math.max(result, Math.min(dist1, dist2));  
            }  
            //index>=0,    headers     house,          house    ， house      0,result    
        }  
        return result;  
    }