[20250319] BOJ / 골드1 / 구간 곱 구하기 / 이강현

Author: lkhyun

lkhyun/202503/19 BOJ 골드1 구간 곱 구하기.md

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+```java
+import java.util.*;
+import java.io.*;
+
+public class Main {
+    static int N;
+    static int M;
+    static int K;
+    static long[] arr;
+    static long[] tree;
+    final static long MOD = 1000000007L;
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        K = Integer.parseInt(st.nextToken());
+        arr = new long[N*4];
+        tree = new long[N*4];
+        
+        for(int i=1;i<=N;i++){
+            arr[i] = Long.parseLong(br.readLine());
+        }
+        init(1,1,N);
+        for(int i=0;i<M+K;i++){
+            st = new StringTokenizer(br.readLine());
+            int option = Integer.parseInt(st.nextToken());
+            int arg1 = Integer.parseInt(st.nextToken());
+            long arg2 = Long.parseLong(st.nextToken());
+            if(option == 1){//수정
+                arr[arg1] = arg2;
+                update(1,1,N,arg1);
+            }else if(option == 2){//구간 곱
+                bw.write(query(1,1,N,arg1,(int)arg2) + "\n");
+            }
+        }
+        bw.close();
+    }
+    public static void init(int num, int start, int end){ //초기화하는 거
+        if(start==end){
+            tree[num] = arr[start];
+        }else{
+            init(num*2, start, (start+end)/2);
+            init(num*2 + 1,(start+end)/2 + 1, end);
+            tree[num] = (tree[num*2] * tree[num*2+1]) % MOD;
+        }
+    }
+    public static long query(int num, int start, int end, int left, int right){ 
+        if(right<start || left>end){
+            return 1;
+        }else if(left<=start && right>=end){
+            return tree[num];
+        }
+        long lsum = query(num*2, start, (start+end)/2, left, right);
+        long rsum = query(num*2+1, (start+end)/2 + 1, end, left, right);
+        return (lsum * rsum) % MOD;
+    }
+    public static long update(int num, int start, int end, int index){// 수정
+        if(start>index || end<index) return tree[num]; //현재 위치가 수정할 곳과 연관이 있는가?
+
+        if(start != end){//현재 위치가 리프노드인가?
+            long left = update(num*2, start,(start+end)/2,index);
+            long right = update(num*2+1,(start+end)/2 + 1,end,index);
+            tree[num] = (left*right) % MOD;
+            return tree[num];
+        }else{
+            tree[num] = arr[start];
+            return tree[num];
+        }
+    }
+}
+```