dp入门

石子合并

#include<iostream>
#include<cstdio>
#include<algorithm>
using namespace std;
int a[300];
int dp[210][210];
int main()
{
    for(int i=1;i<210;i++)
        for(int j=1;j<210;j++)
    {
        dp[i][j]=999999999;
    }

    //////////////////
    for(int i=1;i<210;i++)
    {
        dp[i][i]=0;
    }

    //////////////////////
    int n;
    cin>>n;
    for(int i=1; i<=n; i++)
    {
        cin>>a[i];
    }
    for(int i=2; i<=n; i++)
    {
        for(int j=1; j<=n-i+1; j++)
        {
            for(int k=j; k<=j+i-1-1; k++)
            {
                int sum=0;
                for(int m=j;m<=j+i-1;m++)
                {
                    sum+=a[m];
                }
                dp[j][j+i-1]=min(dp[j][j+i-1],sum+dp[j][k]+dp[k+1][j+i-1]);
            }
        }
    }
    cout<<dp[1][n]<<endl;
}

数位dp

dfs递归

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int a[30];//=
int dp[30][10];
///
long long dfs(int pos,int pre,bool limit)
{
    if(pos==0)
    {
        return 1;
    }
    if(dp[pos][pre]!=-1&&limit==0)
        return dp[pos][pre];
    int up;
    if(limit==true)
    {
        up=a[pos];
    }
    else
        up=9;
    long long ans=0;
    for(int i=0;i<=up;i++)
    {
        if(i==4)
            continue;
        if(pre==6&&i==2)
            continue;
        ans+=dfs(pos-1,i,limit&i==up);
    }
    if(limit==0)
    {
        dp[pos][pre]=ans;
    }
    return ans;
}
long long  solve(int x)
{
    int cnt=0;
    int y;
    while(x>0)
    {
        y=x%10;
        a[++cnt]=y;
        x/=10;
    }
    return dfs(cnt,0,1);
    cout<<dfs(cnt,0,1);
}
int main()
{
    int n,m;
    memset(dp,-1,sizeof(dp));
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        if(n==0&&m==0)
        {
            break;
        }
        solve(m);
        ///cout<<solve(m)<<endl;
        cout<<solve(m)-solve(n-1)<<endl;
    }
    return 0;
}

3.状压dp

#include<iostream>
#include<cstdio>
#define Max 1200
#include<cstring>
int bit[Max];
int save[Max];
long long  ans[10];
long long dp[2][Max];
using namespace std;
long long MOD = 1000000007;
int main()
{
    int cnt=0;
    for(int i=1; i<(1<<10); i++)
    {
        bit[i]=(bit[i>>1]+ (i&1) );
        if(bit[i]%2==0)
        {
            save[cnt++]=i;
        }
    }
    int t;
    scanf("%d",&t);
    while(t--)
    {
        int n,q;
        cin>>n>>q;
        char ch;
        int l,r;
        memset(dp,0,sizeof(dp));
        dp[0][0]=1;
        dp[1][0]=1;
        int flag=0;
        for(int k=0; k<q; k++)
        {
            memset(ans,0,sizeof(ans));
            cin>>ch;
            scanf("%d%d",&l,&r);
            int temp=(1<<(l-1))+(1<<(r-1));
            if(ch=='+')
            {
                for(int i=0; i<cnt&&save[i]<(1<<n); i++)
                {
                    dp[flag^1][ save[i] ]=dp[flag][save[i] ];
                    if( (save[i]&temp)==temp)
                    {
                        dp[flag^1][ save[i] ]+=dp[flag][ save[i]^temp ];
                        dp[flag^1][ save[i] ]%=MOD;
                    }
                    ans[ bit[save[i]]/2 ]+=dp[flag^1][ save[i] ];
                    ans[bit [save[i]]/2]%=MOD;
                }
            }
            else if(ch=='-')
            {
                for(int i=0; i<cnt&&save[i]<(1<<n); i++)
                {
                    dp[flag^1][ save[i] ]=dp[flag][save[i]];
                    if( (save[i]&temp)==temp)
                    {
                        dp[flag^1][ save[i] ]-=dp[flag][ save[i]^temp ];
                        dp[flag^1][ save[i] ]%=MOD;
                    }
                    ans[ bit[save[i]]/2 ]+=dp[flag^1][ save[i] ];
                    ans[bit [save[i]]/2]%=MOD;
                }
            }
            flag^=1;
            for(int i=1; i<=n/2-1; i++)
            {
                printf("%lld ",ans[i]);
            }
            printf("%lld\n",ans[n/2]);
        }
    }
    return 0;
}