diff --git "a/Ukj0ng/202601/31 BOJ G1 \353\266\200\353\266\204\354\210\230\354\227\264\354\235\230 \355\225\251 2.md" "b/Ukj0ng/202601/31 BOJ G1 \353\266\200\353\266\204\354\210\230\354\227\264\354\235\230 \355\225\251 2.md" new file mode 100644 index 00000000..222f0c25 --- /dev/null +++ "b/Ukj0ng/202601/31 BOJ G1 \353\266\200\353\266\204\354\210\230\354\227\264\354\235\230 \355\225\251 2.md" @@ -0,0 +1,94 @@ +``` +import java.io.*; +import java.util.*; + +public class Main { + private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); + private static final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out)); + private static int[] arr; + private static List left, right; + private static int N, S; + + public static void main(String[] args) throws IOException { + init(); + + long answer = 0; + + for (int l : left) { + answer += upperBound(l) - lowerBound(l); + } + + if (S == 0) answer--; + + bw.write(answer + ""); + bw.flush(); + bw.close(); + br.close(); + } + + private static void init() throws IOException { + StringTokenizer st = new StringTokenizer(br.readLine()); + N = Integer.parseInt(st.nextToken()); + S = Integer.parseInt(st.nextToken()); + + arr = new int[N]; + left = new ArrayList<>(); + right = new ArrayList<>(); + + st = new StringTokenizer(br.readLine()); + for (int i = 0; i < N; i++) { + arr[i] = Integer.parseInt(st.nextToken()); + } + + subSum(0, N/2, 0, left); + subSum(N/2, N, 0, right); + + Collections.sort(left); + Collections.sort(right); + } + + private static void subSum(int index, int end, int sum, List list) { + if (index == end) { + list.add(sum); + return; + } + + subSum(index+1, end, sum, list); + subSum(index+1, end, sum+arr[index], list); + } + + private static int upperBound(int target) { + int start = 0; + int end = right.size()-1; + + while (start <= end) { + int mid = start + (end - start) / 2; + + if (target + right.get(mid) > S) { + end = mid-1; + } else { + start = mid+1; + } + } + + return start; + } + + private static int lowerBound(int target) { + int start = 0; + int end = right.size()-1; + + while (start <= end) { + int mid = start + (end - start) / 2; + + if (target + right.get(mid) >= S) { + end = mid-1; + } else { + start = mid+1; + } + } + + return start; + } +} +```