codeforces234C

题意：给你一个序列，问你选定一个K(1 - N-1)值，改变给定序列使得让Ai - Ak  < 0  ,Ak+1 - An  >0 成立，问你最少改多少次

解题思路：这么水的C。。。正反dp找正负就行

解题代码：

// File Name: 234c.cpp
// Author: darkdream
// Created Time: 2014年08月03日 星期日 16时16分35秒

#include<vector>
#include<list>
#include<map>
#include<set>
#include<deque>
#include<stack>
#include<bitset>
#include<algorithm>
#include<functional>
#include<numeric>
#include<utility>
#include<sstream>
#include<iostream>
#include<iomanip>
#include<cstdio>
#include<cmath>
#include<cstdlib>
#include<cstring>
#include<ctime>
#define LL long long

using namespace std;
int a[100005];
int za[100005];
int fa[100005];
int ans = 1e9; 
int main(){
     freopen("input.txt","r",stdin);
     freopen("output.txt","w",stdout);

     int n ;
     scanf("%d",&n);
     memset(za,0,sizeof(za));
     memset(fa,0,sizeof(fa));
     for(int i = 1;i <= n;i ++)
     {
        scanf("%d",&a[i]);
        if(a[i] >= 0)
        {
           za[i] = za[i-1] + 1;   
        }else{
           za[i] = za[i-1];
        }
     }
     for(int i = n;i >= 2; i --)
     {
        if(a[i] <= 0 )
        {
           fa[i] = fa[i+1] +1;
        }else{
           fa[i] = fa[i+1];
        }
        if(fa[i] + za[i-1] < ans)
            ans = fa[i] + za[i-1];
     }
     printf("%d
",ans);
return 0;
}