杭电acm解题报告2001---2099.

				#include 
				#include 
				#include 
				using namespace std;
				
				struct node {
					int l,r;
					node * pl, * pr;
					int count;
				}mem[13000];
				int mem_pos;
				int n,num[5100];
				int anti, ans;
				
				node *
				new_node()
				{
					node * pt = &mem[mem_pos ++];
					memset(pt,0,sizeof(node));
					return pt;
				}
				
				node *
				make_tree(int il, int ir)
				{
					node * root = new_node();
					root ->l = il;
					root ->r = ir;
					if(il != ir) {
						int mid = (il+ir)/2;
						root ->pl = make_tree(il, mid);
						root ->pr = make_tree(mid+1, ir);
					}
					return root;
				}
				
				void
				update(node * root, int num)
				{
					root ->count ++;
					if(root ->l == num && root ->r == num) {
						return ;
					}
					if(root ->pl ->r >= num) {//left
						anti += root ->pr ->count;
						update(root ->pl, num);
					}
					else {//right
						update(root ->pr, num);
					}
				}
				
				int main()
				{
					int i,j;
					while(scanf("%d", &n)==1) {
						anti = 0;
						mem_pos = 0;
						node * root = make_tree(0,n-1);
						for(i=0;i							scanf("%d", num+i);
							update(root, num[i]);
						}
						ans = anti;
						for(i=0;i							anti += n-1 -2*num[i];
							ans = min(ans, anti);
						}
						printf("%d\n",ans);
					}
				}