暴力枚举+DP
虽然是在环上,但最多只需要走一圈...
dp[0][i]表示从1...i从起点逆时针走取完i个的花费,有 dp[0][i]=dp[0][i-k]+dist[i]*2
dp[1][i]表示从i...n从起点顺时针走取完n-i+1个的花费 dp[1][i]=dp[1][i+k]+(L-dist[i])*2
枚举哪些点顺时针哪些点逆时针: ans=min(ans,dp[0][i]+dp[1][i+1]);
然后枚举从哪个点开始走一圈:ans=min(ans,dp[0][max(0,i-K)]+dp[1][i+1]+L);
Delicious Apples
Time Limit: 5000/3000 MS (Java/Others) Memory Limit: 524288/524288 K (Java/Others)
Total Submission(s): 734 Accepted Submission(s): 240
Problem Description
There are n apple
trees planted along a cyclic road, which is L metres
long. Your storehouse is built at position 0 on
that cyclic road.
The ith
tree is planted at position xi,
clockwise from position 0.
There are ai delicious
apple(s) on the ith
tree.
You only have a basket which can contain at most K apple(s).
You are to start from your storehouse, pick all the apples and carry them back to your storehouse using your basket. What is your minimum distance travelled?
1≤n,k≤105,ai≥1,a1+a2+...+an≤105
1≤L≤109
0≤x[i]≤L
There are less than 20 huge testcases, and less than 500 small testcases.
Input
First line: t,
the number of testcases.
Then t testcases
follow. In each testcase:
First line contains three integers, L,n,K.
Next n lines,
each line contains xi,ai.
Output
Output total distance in a line for each testcase.
Sample Input
2 10 3 2 2 2 8 2 5 1 10 4 1 2 2 8 2 5 1 0 10000
Sample Output
18 26
Source
2015 Multi-University Training Contest 2
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/* *********************************************** Author :CKboss Created Time :2015年07月24日 星期五 16时13分36秒 File Name :HDOJ5303.cpp ************************************************ */ #include <iostream> #include <cstdio> #include <cstring> #include <algorithm> #include <string> #include <cmath> #include <cstdlib> #include <vector> #include <queue> #include <set> #include <map> using namespace std; typedef long long int LL; const int maxn=100100; struct Apple { int pos,val; bool operator<(const Apple& apple) const { return pos<apple.pos; } }apple[maxn]; int L,m,K,n; LL dist[maxn]; LL dp[2][maxn]; int main() { //freopen("in.txt","r",stdin); //freopen("out.txt","w",stdout); int T_T; scanf("%d",&T_T); while(T_T--) { memset(dist,0,sizeof(dist)); memset(dp,0,sizeof(dp)); scanf("%d%d%d",&L,&m,&K); for(int i=0,x,y;i<m;i++) { scanf("%d%d",&x,&y); apple[i]=(Apple){x,y}; } n=1; sort(apple,apple+m); for(int i=0,x,y;i<m;i++) { x=apple[i].pos; y=apple[i].val; if(x==0||x==L) continue; while(y--) dist[n++]=x; } for(int i=1;i<n;i++) { dp[0][i]=dp[0][max(0,i-K)]+dist[i]*2; } for(int i=n-1;i>0;i--) { dp[1][i]=dp[1][min(n+1,i+K)]+(L-dist[i])*2; } LL ans=min(dp[0][n-1],dp[1][1]); for(int i=1;i<n;i++) { ans=min(ans,dp[0][i]+dp[1][i+1]); ans=min(ans,dp[0][max(0,i-K)]+dp[1][i+1]+L); } cout<<ans<<endl; } return 0; }
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