2016夏季练习——dp

来源：POJ3280

增加或者减少字符串使得串是回文串

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
int n,len;
char x[2100],ch;
int dp[2100][2100];
int add[30],del[30];

/*转移方程

if(x[i]==x[j])
	dp[i][j] = dp[i+1][j-1];
else
	dp[i][j] =min(dp[i+1][j]+min(add[x[i]-'a'+1],del[x[i]-'a'+1]),dp[i][j-1]+min(add[x[j]-'a'+1],del[x[j]-'a'+1]));
*/
int main(){
	char ch;
	int a,b;
	while(scanf("%d%d",&n,&len)!=EOF){
		//cout<<n<<" "<<len<<endl;
		getchar();
		scanf("%s",x+1);
		//cout<<x+1<<endl;
		getchar();
		//cout<<"start:"<<endl;
		memset(add,0,sizeof(add));
		memset(del,0,sizeof(del));
        for(int i=0;i<n;i++){
		//	cout<<i<<":"<<endl;
			scanf("%c%d%d",&ch,&a,&b);
		//	cout<<ch<<" "<<a<<" "<<b<<endl;
			getchar();
			add[ch-'a'+1] = a;
			del[ch-'a'+1] = b;
        }
        memset(dp,0,sizeof(dp));
		for(int l=1;l<=len;l++){
			for(int i=1;i<=len-l+1;i++){
				int j = i+l-1;
		//		cout<<i<<" "<<j<<" "<<l<<endl;
				if(x[i] == x[j])
					dp[i][j] = dp[i+1][j-1];
				else
					dp[i][j] =min(dp[i+1][j]+min(add[x[i]-'a'+1],del[x[i]-'a'+1]),dp[i][j-1]+min(add[x[j]-'a'+1],del[x[j]-'a'+1]));
			}
		}
		cout<<dp[1][len]<<endl;
	}
	return 0;
}