【POJ3252】 Round Numbers

Problem

https://cn.vjudge.net/problem/20836/origin

Soultion

这道题目让我知道了为什么模板里要有lead记录前导0，一开始没记录偏大。

CODE

/* * @key word:digit DP * @tesed on:POJ3252 16ms * @Author: lhq  * @Date: 2017-08-15 21:18:55  * @Last Modified by:   lhq  * @Last Modified time: 2017-08-15 21:18:55  */#include<iostream>#include<cstdio>#include<cstring>using namespace std;#define ll long longint dp[32][32][32],a[32];int dfs(int len,int num0,int num1,bool lead,bool limit){    if (len==0) return num0>=num1?1:0;    if (!limit && dp[len][num0][num1]!=-1) return dp[len][num0][num1];    int up=limit?a[len]:1;    int ans=0,p=lead?0:1;    ans+=dfs(len-1,num0+p,num1,lead,limit && up==0);    if (up==1) ans+=dfs(len-1,num0,num1+1,false,limit && up==1);    if (!limit) dp[len][num0][num1]=ans;    return ans;}int solve(int x){    int len=0;    while (x)    {        a[++len]=x&1;        x>>=1;    }    return dfs(len,0,0,true,true);}int main(){    memset(dp,-1,sizeof(dp));    int n,m;    while (scanf("%d%d",&n,&m)!=EOF)        printf("%d\n",solve(m)-solve(n-1));    return 0;}