洛谷P1873 Java

题目出处点这里
思路：二分树的高度,注意返回值即可

代码：

package binaryFindAndAnswer;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StreamTokenizer;
import java.util.Arrays;

public class P1873 {

	static int[] arr;
	static int N;
	static int M;

	public static void main(String[] args) throws IOException {
		StreamTokenizer st = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
		st.nextToken();
		N = (int) st.nval;
		arr = new int[N];// 初始化arr
		st.nextToken();
		M = (int) st.nval;
		for (int i = 0; i < N; i++) {
			st.nextToken();
			arr[i] = (int) st.nval;
		}
		Arrays.sort(arr);// 升序
		System.out.println(binary());
	}

	public static int binary() {
		int l = 0, r = arr[N - 1];
		while (l <= r) {
			int mid = l + (r - l) / 2;
			long sum = sum(mid);
			if (sum > M) {
				l = mid + 1;
			}else if (sum < M) {
				r = mid - 1;
			}else {
				return mid;
			}
		}
		return l - 1;//l一定要减一,注意理解
	}
	
	public static long sum(int mid) {
		long sum = 0;
		for (int i = 0; i < arr.length; i++) {
			if (arr[i] > mid) {
				sum = sum + arr[i] - mid;
			}
		}
		return sum;
	}
}