알고리즘 풀이/백준
[백준][Java] 1182번 부분수열의 합 (백트래킹, 브루트포스)
배게
2021. 10. 3. 19:39
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(↓isChanged 패러미터 생략함)
isChanged를 지우기 위해서는 sum이 0일때 공집합의 경우를 1회 빼줘야함;;...
풀이 안 봤으면 isChanged끼고 해야 했을듯
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import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
public class Main {
private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
private static int[] num;
private static int S;
private static int res;
private static void bt(int tot, int pos) {
if(pos == num.length) {
if(tot==S)
res++;
return;
}
bt(tot+num[pos] ,pos+1);
bt(tot, pos+1);
}
public static void main(String[] args) throws IOException{
String[] str = br.readLine().split(" ");
int N = stoi(str[0]);
S = stoi(str[1]);
res = 0;
num = new int[N];
str = br.readLine().split(" ");
for (int i=0; i<N; i++)
num[i] = stoi(str[i]);
bt(0 , 0);
res = (S==0)? --res : res;
bw.write(String.valueOf(res));
bw.flush();
bw.close();
}
private static int stoi(String input) {
return Integer.parseInt(input);
}
}
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cs |
(↓처음에 푼 것)
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import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
public class Main {
private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
private static int[] num;
private static int S;
private static int res;
private static void bt(int tot, int pos, boolean isChanged) {
if(tot == S && isChanged)
res++;
if(pos == num.length)
return;
bt(tot+num[pos] ,pos+1,true);
bt(tot, pos+1, false);
}
public static void main(String[] args) throws IOException{
String[] str = br.readLine().split(" ");
int N = stoi(str[0]);
S = stoi(str[1]);
res = 0;
num = new int[N];
str = br.readLine().split(" ");
for (int i=0; i<N; i++)
num[i] = stoi(str[i]);
bt(0 , 0, false);
bw.write(String.valueOf(res));
bw.flush();
bw.close();
}
private static int stoi(String input) {
return Integer.parseInt(input);
}
}
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cs |