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  1. #include <bits/stdc++.h> 
  2.  
  3. using namespace std;  
  4.  
  5. typedef long long ll;  
  6. typedef pair<int, int> ii;  
  7.  
  8. const int INF = 1e9;  
  9. const ll LINF = 1e18;  
  10.  
  11. const int N = 2e5 + 5; 
  12.  
  13. int n, q; 
  14. int a[N];  
  15.  
  16. struct Node {
  17. 	ll max_subarray, max_pref, max_suf, sum;  
  18.  
  19. 	Node() {
  20. 		max_subarray = max_pref = max_suf = sum = 0; 
  21. 	}
  22.  
  23. 	Node(ll x) {
  24. 		max_subarray = max_pref = max_suf = max(0ll, x);   
  25. 		sum = x;  
  26. 	}
  27.  
  28. 	Node operator+(const Node& other) const {
  29. 		Node res; 
  30. 		res.max_subarray = max({max_subarray, other.max_subarray, max_suf + other.max_pref});
  31. 		res.max_pref = max(max_pref, sum + other.max_pref); 
  32. 		res.max_suf = max(other.max_suf, other.sum + max_suf);   
  33. 		res.sum = sum + other.sum; 
  34. 		return res;   
  35. 	}
  36. }; 
  37.  
  38. Node seg[4 * N]; 
  39.  
  40. void build(int id, int l, int r) {
  41. 	if (l == r) {
  42. 		seg[id] = Node(a[l]); 
  43. 		return; 
  44. 	}
  45. 	int mid = (l + r) >> 1; 
  46. 	build(id * 2, l, mid); 
  47. 	build(id * 2 + 1, mid + 1, r); 
  48. 	seg[id] = seg[id * 2] + seg[id * 2 + 1]; 
  49. }
  50.  
  51. Node get(int id, int l, int r, int u, int v) {
  52. 	if (l > v || r < u) return Node(); 
  53. 	if (u <= l && r <= v) return seg[id]; 
  54. 	int mid = (l + r) >> 1; 
  55. 	return get(id * 2, l, mid, u, v) + get(id * 2 + 1, mid + 1, r, u, v); 
  56. }
  57.  
  58. int main() {
  59. 	ios::sync_with_stdio(false); 
  60. 	cin.tie(nullptr);  	
  61. 	cin >> n >> q;  
  62. 	for (int i = 1; i <= n; i++) cin >> a[i]; 
  63.  
  64. 	build(1, 1, n); 
  65.  
  66. 	while (q--) {
  67. 		int l, r; 
  68. 		cin >> l >> r; 
  69. 		Node ans = get(1, 1, n, l, r); 
  70. 		cout << ans.max_subarray << '\n'; 
  71. 	}
  72. }
Success #stdin #stdout 0.01s 28616KB
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stdin
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8 4
2 5 1 -2 3 -1 -7 1
2 4
2 5
6 7
4 8
stdout
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6
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0
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https://ideone.com/KvYraT
language:
C++14 (gcc 8.3)
created:
39 days ago
visibility:
secret

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