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  1. #include <iostream>
  2. #include<queue>
  3. #include <algorithm>
  4. #include <map>
  5. #include<unordered_map>
  6. #include <set>
  7. #include <fstream>
  8. #include <vector>
  9. #include <math.h>
  10. #include <iomanip>
  11. #include <string>
  12. #include <cstring>
  13. using namespace std;
  14.  
  15. #define ll long long
  16.  
  17. ll mod = 1e9+7;
  18. const int MaxN = 1e5+5;
  19. int MOD = 998244353;
  20. int bit[200000];
  21. ll dem=0;
  22.  
  23. int main() {
  24. 	// freopen(".INP", "r", stdin);
  25. 	//freopen(".OUT", "w", stdout);
  26.  
  27.  
  28.  
  29.  
  30.  
  31.     int n;
  32.     cin >> n;
  33.     int x;
  34.     vector<ll> a;
  35.     map<int, int> mp;
  36.     for(int i=0;i<n;i++){
  37.     	cin >> x;
  38.     	if(x==4){
  39.     		dem++;
  40. 		}
  41. 		else{
  42. 			mp[x]++;
  43. 			a.push_back(x);
  44. 		}
  45. 	}
  46. 	sort(a.begin(),a.end());
  47. 	int l=0,r=a.size()-1;
  48. 	while(l<=r){
  49. 		if(l==r){
  50. 			dem++;
  51. 			break;
  52. 		}
  53. 		if(a[l]+a[r]>4){
  54. 			r--;
  55. 			dem++;
  56. 		}
  57. 		else if(a[l]+a[r]<4){
  58. 			l++;
  59. 			dem++;
  60. 		}
  61. 		else{
  62. 			dem++;
  63. 			l++;
  64. 			r--;
  65. 		}
  66. 	}
  67. 	cout << dem;
  68. 	return 0;
  69. }
Success #stdin #stdout 0.01s 5316KB
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stdin
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https://ideone.com/KzEnkc
language:
C++14 (clang 8.0)
created:
9 days ago
visibility:
public

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