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  1. #include <bits/stdc++.h>
  2. using namespace std ; 
  3.  
  4.  
  5. #define ll long long 
  6. #define fast ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  7. #define fir first 
  8. #define sec second 
  9. #define piint pair < int , int >
  10. #define FOR( i , a , b ) for (int i = (a) , _b = (b) ; i <= _b ; i ++ )  
  11. #define pb push_back 
  12. #define str string 
  13. #define ALL(a) (a).begin() , (a).end() 
  14. #define rep( i , a , b) for (int i = (a) ; i < (b) ; i ++ )
  15. #define ld long double
  16. const int maxn = 1e5;
  17. #define debug 0
  18. #define oo (ll)(1e18)
  19.  
  20. ll a[maxn+3] , g[maxn+3] ; 
  21.  
  22. 	int n ; 
  23. void sub1() {
  24. 	ll ans = -1e18 ;
  25. 	FOR ( i , 1 , n )
  26. 	g[i] = g[i - 1 ] + a[i] ;
  27. 	FOR ( i , 1 , n  ) { 
  28. 		ll x1 , x2 , x3 ; 
  29. 		ll val_1 = -1e18 , val_2 = -1e18 ;
  30. 		FOR ( j , 1 , i  ) 
  31. 		{
  32. 			ll val_of = g[j-1] - ( g[i-1] - g[j-1] ) ;
  33. 			if ( val_of > val_1) {
  34. 				val_1 = val_of ;
  35. 				x1 = j ; 
  36. 			}
  37. 		}
  38. 		x2 = i ; 
  39. 		FOR ( j , i  , n + 1 ) {
  40. 			ll val_of = g[j - 1] - g[i-1] - ( g[n] - g[j-1]) ; 
  41. 			if ( val_of > val_2){
  42. 				val_2 = val_of ; 
  43. 				x3 = j ; 
  44.  
  45. 			}
  46. 		}
  47. 		ans = max ( ans , val_1 + val_2 );
  48. 	}
  49. 	cout << ans ; 
  50. }
  51. ll s[maxn*4 + 3 ] ;
  52. void build ( int id , int l , int r) {
  53. 	if ( l ==r ){
  54. 		s[id] = g[l-1] ;
  55. 		return ;
  56. 	}
  57. 	int m = ( l + r ) >> 1; 
  58. 	build ( id * 2 , l , m ) ;
  59. 	build ( id * 2 + 1, m + 1 , r ) ;
  60. 	s[id] = max ( s[id * 2 ] , s[id * 2 + 1] ) ;
  61. }
  62. ll get ( int id , int l , int r , int u , int v ){
  63.  
  64. 	if ( l > v || r < u ) return -1e18 ;
  65. 	if ( u <= l && r <= v ){
  66. 		return s[id] ;
  67. 	}
  68. 	int m = ( l + r) >> 1 ;
  69. 	return max ( get ( id * 2 , l , m , u , v ) , get ( id * 2 + 1 , m + 1 , r , u , v )) ; 
  70. }
  71. void sub2() {
  72. 	FOR ( i , 1 , n )
  73. 	g[i] = g[i - 1 ] + a[i] ;
  74. 	build ( 1 , 1 , n + 1 ) ; 
  75. 	ll ans_1 = -1e18 ;
  76. 	FOR ( i , 1 , n ){
  77. 		ll val = 2ll * get ( 1 , 1 , n + 1, 1 , i ) - 2ll * g[i-1] + 2ll * get ( 1 , 1 , n + 1, i , n + 1 ) - g[n] ;
  78. 		ans_1 = max ( ans_1 , val ) ; 
  79. 	}
  80. 	cout << ans_1 << '\n'; 
  81. }
  82. void input(){
  83.  
  84. 	cin >> n ;
  85. 	FOR ( i , 1 , n ) cin >> a[i] ; 
  86. 	if ( n < 4 ) return ;
  87. 	else if (n <= 5000 ) sub1() ;
  88. 	else sub2() ;
  89. }
  90. #define name "ditich" 
  91. int main(){
  92.     fast 
  93.     if(fopen(name".INP","r")) {
  94.         freopen (name".INP","r",stdin);
  95.         freopen (name".OUT","w",stdout);
  96.     }
  97.     input() ;
  98.     cerr << "\nTIME: = " << (1.0*clock())/CLOCKS_PER_SEC << '\n';
  99.     return(0) ;
  100. }
Success #stdin #stdout #stderr 0s 5284KB
comments (?)
stdin 
Standard input is empty
stdout 
Standard output is empty
stderr 
TIME: = 0.004531
https://ideone.com/3EM7MD
language:
C++14 (gcc 8.3)
created:
13 days ago
visibility:
public

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