이분탐색 인데 값에서 mid 값을 빼주는 것이 달랐던 문제.
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
public class Main {
static int N;
static int K;
static long[] arr;
static boolean check(long mid) {
long cnt = 0;
for(int i = 0; i < N; i++) {
long val = arr[i] - mid;
if(val > 0) {
cnt += val;
}
}
return cnt >= K;
}
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
StringTokenizer st = new StringTokenizer(br.readLine(), " ");
N = Integer.parseInt(st.nextToken());
K = Integer.parseInt(st.nextToken());
arr = new long[N];
st = new StringTokenizer(br.readLine(), " ");
long max = 0;
for(int i = 0; i < N; i++) {
arr[i] = Integer.parseInt(st.nextToken());
max = Math.max(arr[i], max);
}
long left = 0;
long right = max;
long result = 0;
while(left <= right) {
long mid = (left + right) / 2;
if(check(mid)) {
left = mid + 1;
result = mid;
} else {
right = mid - 1;
}
}
System.out.println(result);
}
}