[20250801] BOJ / P4 / XOR / 이종환

0224LJH/202508/2 BOJ XOR.md

@@ -0,0 +1,175 @@
+```java
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.StringTokenizer;
+
+
+public class Main {
+
+    static final int UPDATE = 1;
+    static final int QUERY = 2;
+    static int size, changeCnt, sumCnt,queryCnt;
+    static long[] input;
+    static StringBuilder sb = new StringBuilder();
+    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+
+    static class SegmentTree{
+        private long[] lazy; //레이지 프로파게이션
+        public long[] tree;
+        private int size; // 원본 배열의 크기
+
+        public SegmentTree(long[] arr){
+            size = arr.length;
+            this.lazy = new long[size*4];
+            this.tree = new long[size*4];
+            build(arr,1,0,size-1);
+        }
+
+        private void build(long[] arr, int node, int startIdx, int endIdx){
+            if(startIdx == endIdx){
+                tree[node] = arr[startIdx];
+                return;
+            }
+
+            int mid = (startIdx + endIdx)/2;
+            build(arr,node*2,startIdx,mid);
+            build(arr,node*2+1,mid+1,endIdx);
+            tree[node] = tree[node*2]^tree[node*2+1];
+        }
+
+        public void updateRange(int startIdx , int endIdx,  long k ){
+            updateRange(1, 0, size-1, startIdx, endIdx, k);
+        }
+
+        private void updateRange(int node,int left,int right, int startIdx , int endIdx,  long k){
+            updateLazy(node, left, right);
+
+            if ( left > endIdx  || right < startIdx) return; //현 구간과 업데이트 구간이 아예 안겹칩
+
+            if (left >= startIdx && right <= endIdx){ // 완전히 포함되는 경우
+                // XOR의 특성: 구간 길이가 홀수일 때만 실제로 값이 변함
+                int rangeLength = right - left + 1;
+                if (rangeLength % 2 == 1) {
+                    tree[node] ^= k;
+                }
+
+                // 리프 노드가 아니라면 lazy 전파
+                if (left != right) {
+                    lazy[2*node] ^= k;
+                    lazy[2*node+1] ^= k;
+                }
+                return;
+            }
+
+            int mid = (left+right)/2;
+
+            updateRange(node*2, left, mid, startIdx, endIdx, k);
+            updateRange(node*2+1, mid+1, right, startIdx, endIdx, k);
+
+            updateLazy(node*2, left, mid);
+            updateLazy(node*2+1, mid+1,right);
+            tree[node] = tree[node*2]^tree[node*2+1];
+        }
+
+        private void updateLazy(int node, int left, int right){
+            if (lazy[node] == 0) return;
+
+            long k = lazy[node];
+            // XOR의 특성: 구간 길이가 홀수일 때만 실제로 값이 변함
+            int rangeLength = right - left + 1;
+            if (rangeLength % 2 == 1) {
+                tree[node] ^= k;
+            }
+
+            if (left != right){
+                lazy[node*2] ^= k;
+                lazy[node*2+1] ^= k;
+            }
+            lazy[node] = 0;
+        }
+
+        public long query(int startIdx, int endIdx){
+            return query(1,0, size-1, startIdx, endIdx);
+        }
+
+        private long query(int node , int left, int right, int startIdx , int endIdx){
+            updateLazy(node, left, right);
+            if ( left > endIdx  || right < startIdx) return 0;
+            if (left >= startIdx && right <= endIdx) return tree[node];
+
+            int mid = (left+right)/2;
+            return query(node*2, left, mid, startIdx, endIdx)^query(node*2+1, mid+1, right, startIdx, endIdx);
+        }
+    }
+
+
+
+    public static void main(String[] args) throws IOException {
+        init();
+        process();
+        print();
+    }
+
+    private static void init() throws IOException {
+        size = Integer.parseInt(br.readLine());
+        input = new long[size];
+
+
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        for (int i = 0; i < size; i++) {
+            input[i] = Long.parseLong(st.nextToken());
+        }
+
+        queryCnt =  Integer.parseInt(br.readLine());
+
+    }
+
+    private static void process() throws IOException {
+
+        SegmentTree tree = new SegmentTree(input);
+
+        for (int i = 0; i < queryCnt; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            int order = Integer.parseInt(st.nextToken());
+            int start = Integer.parseInt(st.nextToken());
+            int end = Integer.parseInt(st.nextToken());
+
+
+            if (order == UPDATE) {
+                long plus = Long.parseLong(st.nextToken());
+                tree.updateRange(start, end, plus);
+            } else sb.append(tree.query(start, end)).append("\n");
+
+
+            int power = 2;
+            for (int j = 1; j < tree.tree.length; j++) {
+                if (j == power) {
+                    System.out.println();
+                    power *= 2;
+                }
+                System.out.print(tree.tree[j] +" ");
+            }
+            System.out.println();
+
+
+            power = 2;
+            for (int j = 1; j < tree.tree.length; j++) {
+                if (j == power) {
+                    System.out.println();
+                    power *= 2;
+                }
+                System.out.print(tree.lazy[j] +" ");
+            }
+            System.out.println();
+        }
+
+    }
+
+
+    private static void print() {
+        System.out.println(sb.toString());
+
+    }
+}
+```

0224LJH/202508/3 BOJ 여행 가자.md

@@ -0,0 +1,95 @@
+```java
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.StringTokenizer;
+
+
+public class Main {
+
+
+    static StringBuilder sb = new StringBuilder();
+    static int cityCnt,planCityCnt;
+    static int[][] arr;
+    static int[] plan,parent;
+
+
+    public static void main(String[] args) throws IOException {
+        init();
+        process();
+        print();
+    }
+
+    private static void init() throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        cityCnt = Integer.parseInt(br.readLine());
+        planCityCnt = Integer.parseInt(br.readLine());
+        arr = new int[cityCnt][cityCnt];
+        parent = new int[cityCnt];
+        for (int i = 0; i < cityCnt; i++) {
+            parent[i] = i;
+        }
+        plan = new int[planCityCnt];
+
+        for (int i = 0; i < cityCnt; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            for (int j = 0; j < cityCnt; j++) {
+                arr[i][j] = Integer.parseInt(st.nextToken());
+            }
+        }
+
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        for (int i = 0; i < planCityCnt; i++) {
+            plan[i] = Integer.parseInt(st.nextToken())-1;
+        }
+
+    }
+
+    private static void process() throws IOException {
+        for (int i = 0; i < cityCnt; i++) {
+            for (int j = 0; j < cityCnt; j++) {
+                if (arr[i][j] == 1) union(i,j);
+            }
+        }
+
+        for (int i = 1; i < planCityCnt; i++) {
+            int preRoot = find(plan[i-1]);
+            int curRoot = find(plan[i]);
+            if (preRoot != curRoot) {
+                System.out.println("NO");
+                return;
+            }
+        }
+
+        System.out.println("YES");
+
+    }
+
+    private static void union(int a, int b) {
+        int aRoot = find(a);
+        int bRoot = find(b);
+
+        if (aRoot == bRoot) return;
+
+        if (aRoot > bRoot) {
+            parent[bRoot] = aRoot;
+        } else {
+            parent[aRoot] = bRoot;
+        }
+
+    }
+
+    private static int find(int x) {
+        if (x == parent[x]) return x;
+
+        return parent[x] = find(parent[x]);
+    }
+
+
+
+    private static void print() {
+        System.out.print(sb.toString());
+    }
+}
+```