【HDOJ】4261 Estimation
挺不错的一道题，基本思路是dp。关键点是如何求区间内的Sigma|A_i-B_i|。
线段树做TLE了，优先队列可以过。
1 /* 4261 */ 2 #include <iostream> 3 #include <sstream> 4 #include <string> 5 #include <map> 6 #include <queue> 7 #include <set> 8 #include <stack> 9 #include <vector> 10 #include <deque> 11 #include <algorithm> 12 #include <cstdio> 13 #include <cmath> 14 #include <ctime> 15 #include <cstring> 16 #include <climits> 17 #include <cctype> 18 #include <cassert> 19 #include <functional> 20 #include <iterator> 21 #include <iomanip> 22 using namespace std; 23 //#pragma comment(linker,"/STACK:102400000,1024000") 24 25 #define sti set<int> 26 #define stpii set<pair<int, int> > 27 #define mpii map<int,int> 28 #define vi vector<int> 29 #define pii pair<int,int> 30 #define vpii vector<pair<int,int> > 31 #define rep(i, a, n) for (int i=a;i<n;++i) 32 #define per(i, a, n) for (int i=n-1;i>=a;--i) 33 #define clr clear 34 #define pb push_back 35 #define mp make_pair 36 #define fir first 37 #define sec second 38 #define all(x) (x).begin(),(x).end() 39 #define SZ(x) ((int)(x).size()) 40 #define lson l, mid, rt<<1 41 #define rson mid+1, r, rt<<1|1 42 43 const int INF = 1e9; 44 const int maxn = 2005; 45 const int maxm = 30; 46 int n, m; 47 int a[maxn]; 48 int dp[maxm][maxn]; 49 int dif[maxn][maxn]; 50 51 void solve() { 52 int tmp; 53 54 rep(i, 1, n+1) { 55 priority_queue<int> q; 56 priority_queue<int, vi, greater<int> > Q; 57 58 int ls, rs; 59 int ln, rn; 60 int x, xx; 61 int l = 0; 62 63 ln = rn = 0; 64 ls = rs = 0; 65 rep(j, i, n+1) { 66 ++l; 67 x = a[j]; 68 if (l & 1) { 69 ++ln; 70 if (rn && Q.top()<x) { 71 xx = Q.top(); 72 Q.pop(); 73 q.push(xx); 74 ls += xx; 75 Q.push(x); 76 rs += x - xx; 77 } else { 78 q.push(x); 79 ls += x; 80 } 81 82 x = q.top(); 83 tmp = rs - ls + x; 84 dif[i][j] = tmp; 85 } else { 86 ++rn; 87 if (q.top() > x) { 88 xx = q.top(); 89 q.pop(); 90 Q.push(xx); 91 rs += xx; 92 q.push(x); 93 ls += x - xx; 94 } else { 95 Q.push(x); 96 rs += x; 97 } 98 99 x = q.top(); 100 tmp = rs - ls; 101 dif[i][j] = tmp; 102 } 103 } 104 } 105 106 rep(j, 1, n+1) { 107 dp[1][j] = dif[1][j]; 108 } 109 110 rep(i, 2, m+1) { 111 rep(j, i, n+1) { 112 dp[i][j] = INF; 113 rep(k, i-1, j) { 114 dp[i][j] = min(dp[i][j], dp[i-1][k]+dif[k+1][j]); 115 } 116 } 117 } 118 119 printf("%d\n", dp[m][n]); 120 } 121 122 int main() { 123 ios::sync_with_stdio(false); 124 #ifndef ONLINE_JUDGE 125 freopen("data.in", "r", stdin); 126 freopen("data.out", "w", stdout); 127 #endif 128 129 while (scanf("%d %d", &n, &m)!=EOF && (n||m)) { 130 rep(i, 1, n+1) { 131 scanf("%d", &a[i]); 132 } 133 solve(); 134 } 135 136 #ifndef ONLINE_JUDGE 137 printf("time = %d.\n", (int)clock()); 138 #endif 139 140 return 0; 141 }
数据生成器。
1 from random import randint, shuffle 2 import shutil 3 import string 4 5 6 def GenDataIn(): 7 with open("data.in", "w") as fout: 8 t = 22 9 bound = 10**4 10 for tt in xrange(t): 11 n = randint(1800, 2000) 12 k = randint(1, 25) 13 fout.write("%d %d\n" % (n, k)) 14 dataList = [] 15 for i in xrange(n): 16 x = randint(-bound, bound) 17 dataList.append(x) 18 fout.write(" ".join(map(str, dataList)) + "\n") 19 fout.write("0 0\n") 20 21 22 def MovDataIn(): 23 desFileName = "F:\eclipse_prj\workspace\hdoj\data.in" 24 shutil.copyfile("data.in", desFileName) 25 26 27 if __name__ == "__main__": 28 GenDataIn() 29 MovDataIn()
