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：
1 // File Name: 234c.cpp 2 // Author: darkdream 3 // Created Time: 2014年08月03日 星期日 16时16分35秒 4 5 #include<vector> 6 #include<list> 7 #include<map> 8 #include<set> 9 #include<deque> 10 #include<stack> 11 #include<bitset> 12 #include<algorithm> 13 #include<functional> 14 #include<numeric> 15 #include<utility> 16 #include<sstream> 17 #include<iostream> 18 #include<iomanip> 19 #include<cstdio> 20 #include<cmath> 21 #include<cstdlib> 22 #include<cstring> 23 #include<ctime> 24 #define LL long long 25 26 using namespace std; 27 int a[100005]; 28 int za[100005]; 29 int fa[100005]; 30 int ans = 1e9; 31 int main(){ 32 freopen("input.txt","r",stdin); 33 freopen("output.txt","w",stdout); 34 35 int n ; 36 scanf("%d",&n); 37 memset(za,0,sizeof(za)); 38 memset(fa,0,sizeof(fa)); 39 for(int i = 1;i <= n;i ++) 40 { 41 scanf("%d",&a[i]); 42 if(a[i] >= 0) 43 { 44 za[i] = za[i-1] + 1; 45 }else{ 46 za[i] = za[i-1]; 47 } 48 } 49 for(int i = n;i >= 2; i --) 50 { 51 if(a[i] <= 0 ) 52 { 53 fa[i] = fa[i+1] +1; 54 }else{ 55 fa[i] = fa[i+1]; 56 } 57 if(fa[i] + za[i-1] < ans) 58 ans = fa[i] + za[i-1]; 59 } 60 printf("%d ",ans); 61 return 0; 62 }