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【poj1738】 An old Stone Game

http://poj.org/problem?id=1738 (题目链接)

题意

  一排n堆石子,合并两堆石子的代价为两堆石子总数之和。问将所有石子合并为一堆所需要的最小代价。

Solution

  本来想用刚学的四边形不等式练练手的,没想到n的范围竟然是50000,数组都开不下啊。。只好去看了下那个不明觉厉的GarsiaWachs。具体做法参见:http://blog.csdn.net/acdreamers/article/details/18043897。也真的是奇葩。。

代码

// poj1738#include<algorithm>#include<iostream>#include<cstdlib>#include<cstring>#include<cstdio>#include<cmath>#include<set>#define LL long long#define inf 2147483640#define Pi acos(-1.0)#define free(a) freopen(a".in","r",stdin),freopen(a".out","w",stdout);using namespace std;const int maxn=50010;int a[maxn],n,tot,ans;void unions(int x) {	int tmp=a[x]+a[x-1];	ans+=tmp;	for (int i=x;i<tot;i++) a[i]=a[i+1];	int j;	for (j=x-1;a[j-1]<tmp && j>1;j--) a[j]=a[j-1];	a[j]=tmp;tot--;	for (int d=tot-j;j>2 && a[j-2]<=a[j];d=tot-j) {		unions(j-1);		j=tot-d;	}}int main() {	while (scanf("%d",&n)!=EOF && n) {		ans=tot=0;		for (int i=1;i<=n;i++) scanf("%d",&a[i]);		for (int i=1;i<=n;i++) {			a[++tot]=a[i];			while (tot>2 && a[tot-2]<=a[tot]) unions(tot-1);		}		while (tot>1) unions(tot);		printf("%d\n",ans);	}	return 0;}

  

【poj1738】 An old Stone Game