USACO Section 2.1: Sorting a Three-Valued Sequence

简单题

 1 /*

 2 ID: leetcod3

 3 PROG: sort3

 4 LANG: C++

 5 */

 6 #include <iostream>

 7 #include <fstream>

 8 #include <string>

 9 #include <map>

10 #include <vector>

11 #include <set>

12 #include <algorithm>

13 #include <queue>

14 #include <cmath>

15 #include <list>

16 #include <cstring>

17 #include <cstdlib>

18 #include <limits>

19 #include <stack>

20 

21 using namespace std;

22 

23 ofstream fout ("sort3.out");

24 ifstream fin ("sort3.in");

25 

26 int N;

27 

28 int main()

29 {

30     fin >> N;

31     vector<int> input(N);

32     int one, two, three;

33     one = two = three = 0;

34     for (int i = 0; i < N; ++i) {

35         fin >> input[i];

36         if (input[i] == 1) one++;

37         else if (input[i] == 2) two++;

38         else three++;

39     }

40     int pos[4][4] = {0};

41     for (int i = 0; i < one; ++i) pos[1][input[i]]++;

42     for (int i = one; i < one+two; ++i) pos[2][input[i]]++;

43     for (int i = one+two; i < N; ++i) pos[3][input[i]]++;

44     for (int i = 1; i < 4; ++i) {

45         //for (int j = 1; j < 4; ++j) cout << pos[i][j] << " ";

46         //cout << endl;

47     }

48     int ans = 0;

49     for (int i = 1; i <= 3; ++i) {

50         for (int j = i; j <= 3; ++j) {

51             if (i == j) continue;

52             int tmp = min(pos[i][j], pos[j][i]);

53             ans += tmp;

54             pos[i][j] -= tmp;

55             pos[j][i] -= tmp;

56         }

57     }

58     int tmp = 0;

59     //cout << ans << endl;

60     for (int i = 1; i <= 3; ++i) {

61         for (int j = 1; j <= 3; ++j) {

62             if (i == j) continue;

63             tmp += pos[i][j];

64         }

65     }

66     //cout << tmp << endl;

67     ans += tmp / 3 * 2;

68     fout << ans << endl;

69 

70     return 0;

71 }