hdu How to Type

感觉这道dp题还是有点技巧的，此题设置了两个数组：open[]和close[]，分别用来记录capslock一直开启状态和一直关闭状态下的最少输入次数。此时只要判断字母的大小写，选用最优子结构即可。状态转移方程为：

str[i]是小写字母：

open[i]=min(open[i-1]+2,close[i-1]+2);
close[i]=min(close[i-1]+1,open[i-1]+2);

str[i]是大写字母：

open[i]=min(open[i-1]+1,close[i-1]+2);
close[i]=min(close[i-1]+2,open[i-1]+2);

#include"iostream"
#include"stdio.h"
#include"string.h"
#include"ctype.h"
#define mx 1000
using namespace std;
char str[mx];
int open[mx],close[mx];
int min(int a,int b)
{
    return a<b?a:b;
}
int main()
{
    int i,j,t;
    cin>>t;
    getchar();
    while(t--)
    {
        memset(open,0,sizeof(open));
        memset(close,0,sizeof(close));
        cin>>str;
        if(islower(str[0])) {open[0]=2;close[0]=1;}
        else  {open[0]=2;close[0]=2;}
        for(i=1;str[i]!=‘\0‘;i++)
        {
            if(islower(str[i]))
            {
                open[i]=min(open[i-1]+2,close[i-1]+2);
                close[i]=min(close[i-1]+1,open[i-1]+2);
            }
            else
            {
                open[i]=min(open[i-1]+1,close[i-1]+2);
                close[i]=min(close[i-1]+2,open[i-1]+2);
            }
        }
        cout<<close[i-1]<<endl;
    }
    return 0;
}