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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define int              long long int
  4. #define double           long double
  5. #define print(a)         for(auto x : a) cout << x << " "; cout << endl
  6.  
  7.  
  8. const int M = 1000000007;
  9. const int N = 3e5+9;
  10. const int INF = 2e9+1;
  11. const int LINF = 2000000000000000001;
  12.  
  13. inline int power(int a, int b, int mod=M) {
  14.     int x = 1;
  15.     a %= mod;
  16.     while (b) {
  17.         if (b & 1) x = (x * a) % mod; 
  18.         a = (a * a) % mod;
  19.         b >>= 1;
  20.     }
  21.     return x;
  22. }
  23.  
  24.  
  25. //_ ***************************** START Below *******************************
  26.  
  27.  
  28.  
  29.  
  30. vector<int> a;
  31.  
  32. //* Dp + greedy kadane 
  33.  
  34. int consistency1(int n){
  35.  
  36. 	if(n==1) return a[0];
  37.  
  38. 	int z = 0;
  39. 	int neg = 0;
  40. 	int prod = 1;
  41.  
  42. 	for(int i=0; i<n; i++){
  43. 	    if(a[i] < 0) neg++;
  44. 	    else if(a[i] == 0) z++;
  45. 	    prod *= a[i];
  46. 	}
  47. 	if( !(neg & 1) && z == 0) return prod;
  48.  
  49. 	vector<int> prefix(n+1, 1);
  50. 	vector<int> pMaxi(n+1, INT32_MIN);
  51. 	int maxi = INT32_MIN;
  52. 	for(int i=0; i<n; i++){
  53. 	    if(a[i] != 0){
  54. 	        prefix[i+1] = prefix[i] * a[i];
  55. 	        maxi = max(maxi, prefix[i+1]);
  56. 	        pMaxi[i+1] = maxi;
  57. 	    }
  58. 	}
  59.  
  60. 	vector<int> sufix(n+1, 1);
  61. 	vector<int> sMaxi(n+1, INT32_MIN);
  62.  
  63. 	maxi = INT32_MIN;
  64. 	for(int i=n-1; i>=0; i--){
  65. 	    if(a[i] != 0){
  66. 	        sufix[i] = sufix[i+1] * a[i];
  67. 	        maxi = max(maxi, sufix[i]);
  68. 	        sMaxi[i] = maxi;
  69. 	    }
  70. 	}
  71.  
  72. 	int ans = INT32_MIN;
  73. 	for(int i=0; i<n; i++){
  74. 	    int left = pMaxi[i];
  75. 	    int right = sMaxi[i+1];
  76. 	    if(a[i] <= 0){
  77. 	        ans = max(ans, max(left, right));
  78. 	    }
  79. 	}
  80.  
  81. 	if(z > 0)   ans = max(ans, 0LL);
  82. 	return ans;
  83.  
  84. }
  85.  
  86.  
  87.  
  88.  
  89.  
  90. //* Greedy Kadane
  91.  
  92. int consistency2(int n){
  93.  
  94. 	int maxi = INT32_MIN;
  95. 	int prod = 1;
  96.  
  97. 	for(int i=0; i<n; i++){
  98. 		prod *= a[i];
  99. 		maxi = max(maxi, prod);
  100.  
  101. 	    if(prod == 0){
  102. 	        prod = 1;
  103. 	    }
  104. 	}
  105.  
  106.  
  107. 	prod = 1;
  108. 	for(int i=n-1; i>=0; i--){
  109. 		prod *= a[i];
  110. 		maxi = max(maxi, prod);
  111. 		if(prod == 0){
  112. 			prod = 1;
  113. 		}
  114. 	}
  115.  
  116. 	return maxi;
  117. }
  118.  
  119.  
  120.  
  121.  
  122.  
  123. //* Optimized 1 loop 
  124.  
  125. int consistency3(int n){
  126.  
  127. 	int maxi1 = INT32_MIN;
  128. 	int maxi2 = INT32_MIN;
  129. 	int prod1 = 1;
  130. 	int prod2 = 1;
  131.  
  132. 	int ans = INT32_MIN;
  133.  
  134. 	for(int i=0; i<n; i++){
  135. 		prod1 *= a[i];
  136. 		prod2 *= a[n-i-1];
  137.  
  138. 		maxi1 = max(maxi1, prod1);
  139. 		maxi2 = max(maxi2, prod2);
  140.  
  141. 		ans = max(ans, max(maxi1, maxi2));
  142.  
  143. 	    if(prod1 == 0){
  144. 	        prod1 = 1;
  145. 	    }
  146. 	    if(prod2 == 0){
  147. 	    	prod2 = 1;
  148. 	    }
  149. 	}
  150.  
  151.  
  152. 	return ans;
  153. }
  154.  
  155.  
  156.  
  157.  
  158.  
  159.  
  160.  
  161.  
  162.  
  163.  
  164.  
  165.  
  166.  
  167.  
  168.  
  169.  
  170.  
  171. int practice(int n){
  172.  
  173.  
  174.     return 0;
  175. }
  176.  
  177.  
  178.  
  179.  
  180.  
  181. void solve() {
  182.  
  183.     int n;
  184.     cin>> n;
  185.  
  186.     a.resize(n);
  187.     for(int i=0; i<n; i++) cin >> a[i];
  188.  
  189.     cout << consistency1(n) << " " << consistency2(n) << " " << consistency3(n) << endl;
  190.  
  191.  
  192. }
  193.  
  194.  
  195.  
  196.  
  197.  
  198. int32_t main() {
  199.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  200.  
  201.     int t = 1;
  202.     // cin >> t;
  203.     while (t--) {
  204.         solve();
  205.     }
  206.  
  207.     return 0;
  208. }
Success #stdin #stdout 0.01s 5312KB
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https://ideone.com/MEwUU6
language:
C++14 (gcc 8.3)
created:
3 days ago
visibility:
public

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