简单题
1
/*
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ID: leetcod3
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PROG: sort3
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LANG: C++
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*/
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#include <iostream>
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#include <fstream>
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#include <
string
>
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#include <map>
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#include <vector>
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#include <
set
>
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#include <algorithm>
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#include <queue>
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#include <cmath>
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#include <list>
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#include <cstring>
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#include <cstdlib>
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#include <limits>
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#include <stack>
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using
namespace
std;
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ofstream fout (
"
sort3.out
"
);
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ifstream fin (
"
sort3.in
"
);
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int
N;
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int
main()
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{
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fin >>
N;
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vector<
int
>
input(N);
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int
one, two, three;
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one = two = three =
0
;
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for
(
int
i =
0
; i < N; ++
i) {
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fin >>
input[i];
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if
(input[i] ==
1
) one++
;
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else
if
(input[i] ==
2
) two++
;
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else
three++
;
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}
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int
pos[
4
][
4
] = {
0
};
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for
(
int
i =
0
; i < one; ++i) pos[
1
][input[i]]++
;
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for
(
int
i = one; i < one+two; ++i) pos[
2
][input[i]]++
;
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for
(
int
i = one+two; i < N; ++i) pos[
3
][input[i]]++
;
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for
(
int
i =
1
; i <
4
; ++
i) {
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//
for (int j = 1; j < 4; ++j) cout << pos[i][j] << " ";
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//
cout << endl;
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}
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int
ans =
0
;
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for
(
int
i =
1
; i <=
3
; ++
i) {
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for
(
int
j = i; j <=
3
; ++
j) {
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if
(i == j)
continue
;
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int
tmp =
min(pos[i][j], pos[j][i]);
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ans +=
tmp;
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pos[i][j] -=
tmp;
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pos[j][i] -=
tmp;
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}
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}
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int
tmp =
0
;
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//
cout << ans << endl;
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for
(
int
i =
1
; i <=
3
; ++
i) {
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for
(
int
j =
1
; j <=
3
; ++
j) {
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if
(i == j)
continue
;
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tmp +=
pos[i][j];
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}
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}
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//
cout << tmp << endl;
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ans += tmp /
3
*
2
;
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fout << ans <<
endl;
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return
0
;
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}
