algorithm-implementation/segmented_tree.cpp at master · shuvokhalid173/algorithm-implementation · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
#include <bits/stdc++.h>

using namespace std;

const int N = 1234;
int arr[N];
int seg[N * 3];

void construct (int n , int left , int right) {
	if (left == right) {seg[n] = arr[left]; return ;}
	int ll = n * 2;
	int rr = ll + 1;
	int mid = (left + right) / 2;
	construct (ll , left , mid);
	construct (rr , mid + 1 , right);
	seg[n] = seg[ll] + seg[rr];
}

int get_sum (int n , int left , int right , int start , int end) {
	if (left > end || right < start) return 0;
	if (left >= start && right <= end) return seg[n];
	int ll = n * 2;
	int rr = ll + 1;
	int mid = (left + right) / 2;
	int left_p = get_sum (ll , left , mid , start , end);
	int right_p = get_sum (rr , mid + 1 , right , start , end);
	return left_p + right_p;
}

void update_value (int n , int left , int right , int index , int value) {
	if (left > index || right < index) return ;
	if (left >= index && right <= index) {seg[n] = value; return ;}
	int ll = n * 2;
	int rr = ll + 1;
	int mid = (left + right) / 2;
	update_value (ll , left , mid , index , value);
	update_value (rr , mid + 1 , right , index , value);
	seg[n] = seg[ll] + seg[rr];
}

int main () {
	ios_base::sync_with_stdio (0);
	cin.tie(); cout.tie();
	int n; cin >> n;
	for (int i = 1; i <= n; i++)
		cin >> arr[i];
	construct (1 , 1 , n);
	int noq; cin >> noq;
	for (int i = 0; i < noq; i++) {
		int ind , upd ;
		cin >> ind >> upd;
		update_value (1 , 1 , n , ind , upd);
		int llf , lri;
		cin >> llf  >> lri;
		cout << get_sum (1 , 1 , n , llf , lri) << endl;
	}
}