「BZOJ1679」[Usaco2005 Jan] Moo Volume 牛的呼声
Description
Farmer John has received a noise complaint from his neighbor, Farmer Bob, stating that his cows are making too much noise. FJ’s N cows (1 <= N <= 10,000) all graze at various locations on a long one-dimensional pasture. The cows are very chatty animals. Every pair of cows simultaneously carries on a conversation (so every cow is simultaneously MOOing at all of the N-1 other cows). When cow i MOOs at cow j, the volume of this MOO must be equal to the distance between i and j, in order for j to be able to hear the MOO at all. Please help FJ compute the total volume of sound being generated by all N*(N-1) simultaneous MOOing sessions.
Input
* Line 1: N * Lines 2..N+1: The location of each cow (in the range 0..1,000,000,000).
Output
* Line 1: A single integer, the total volume of all the MOOs.
Sample Input
1
5
3
2
4
INPUT DETAILS:
There are five cows at locations 1, 5, 3, 2, and 4.
Sample Output
OUTPUT DETAILS:
Cow at 1 contributes 1+2+3+4=10, cow at 5 contributes 4+3+2+1=10, cow at 3
contributes 2+1+1+2=6, cow at 2 contributes 1+1+2+3=7, and cow at 4
contributes 3+2+1+1=7. The total volume is (10+10+6+7+7) = 40.
题解
排序以后dp。。
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#include<iostream> #include<cstdio> #include<algorithm> #include<cmath> #define ll long long using namespace std; inline int read() { int x=0;char ch=getchar(); while(ch<'0'||ch>'9')ch=getchar(); while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();} return x; } int n; ll a[10005],sum[10005],f[10005]; int main() { n=read(); for(int i=1;i<=n;i++) a[i]=read(); sort(a+1,a+n+1); for(int i=1;i<=n;i++) { sum[i]=sum[i-1]+a[i]; f[i]=f[i-1]+(a[i]*i)-sum[i]; } printf("%lld",f[n]*2); return 0; } |
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