Bzoj2708 [VIOLET 1] puppet

The first thing that comes to mind is greed... Definitely not... T

Then we found that it was actually DP-enabled... However, we need to sort them first.

If f [I] indicates that the first puppet has to lose a few at worst

F [I] = max (F [J] + calc (J + 1, I) where j <I

 

The calc (x, y) function compute can discard a maximum of several matching functions from the X to the Y puppet. The method is as follows:

Hzwer: "enumeration can throw the number k to determine whether the remaining can match each other, cannot return K-1

And whether the thrown out can match each other, can match return K-1"

 

 1 /************************************************************** 2     Problem: 2708 3     User: rausen 4     Language: C++ 5     Result: Accepted 6     Time:24 ms 7     Memory:804 kb 8 ****************************************************************/ 9  10 #include <cstdio>11 #include <cstring>12 #include <algorithm>13  14 using namespace std;15 const int N = 55;16 int n, a[N], f[N];17  18 inline int read(){19     int x = 0, sgn = 1;20     char ch = getchar();21     while (ch < ‘0‘ || ch > ‘9‘){22         if (ch == ‘-‘) sgn = -1;23         ch = getchar();24     }25     while (ch >= ‘0‘ && ch <= ‘9‘){26         x = x * 10 + ch - ‘0‘;27         ch = getchar();28     }29     return sgn * x;30 }31  32 int calc(int x, int y){33     int i, k;34     for (k = 1; k <= y - x + 1; ++k){35         for (i = k; i <= y - x; ++i)36             if (abs(a[i + x] - a[i + x - k]) > 1) return k - 1;37         if (abs(a[x + k - 1] - a[y - k + 1]) <= 1) return k - 1;38     }39     return y - x + 1;40 }41  42 int main(){43     int i, j;44     while (scanf("%d", &n) != EOF){45         for (i = 1; i <= n; ++i)46             scanf("%d", a + i);47         sort(a + 1, a + n + 1);48         memset(f, 0, sizeof(f));49         for (i = 1; i <= n; ++i)50             for (j = 0; j < i; ++j)51                 f[i] = max(f[i], f[j] + calc(j + 1, i));52         printf("%d\n", f[n]);53     }54     return 0;55 }

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Bzoj2708 [VIOLET 1] puppet