zoj 3816 2014牡丹江网赛 DFS

来源：互联网发布：淘宝和京东创始人编辑：程序博客网时间：2024/04/27 21:35

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=5348

写的真痛苦，换了好几种写法还是不行，贪心贪不对.......

参考了http://www.cnblogs.com/njczy2010/p/3961614.html

思路：
首先枚举左边的每一位，然后枚举右边有几位和这一位相同，写着还是有些细节要注意的

//#pragma comment(linker, "/STACK:102400000,102400000")#include <cstdio>#include <cstring>#include <algorithm>#include <string>#include <iostream>#include <iomanip>#include <cmath>#include <map>#include <set>#include <queue>using namespace std;#define ls(rt) rt*2#define rs(rt) rt*2+1#define ll long long#define ull unsigned long long#define rep(i,s,e) for(int i=s;i<e;i++)#define repe(i,s,e) for(int i=s;i<=e;i++)#define CL(a,b) memset(a,b,sizeof(a))#define IN(s) freopen(s,"r",stdin)#define OUT(s) freopen(s,"w",stdout)const ll ll_INF = ((ull)(-1))>>1;const double EPS = 1e-8;const int INF = 100000000;const int MAXN = 30;ll n;char num[MAXN];char leftn[MAXN],rightn[MAXN];int lenn;void init(){    sprintf(num,"%lld",n);    CL(leftn,0);    CL(rightn,0);    lenn=strlen(num);    for(int i=0;i<lenn;i++)        num[i]-='0';}ll cal(int l, int r){    ll ret=0;    for(int i=0;i<l;i++)        ret=ret*10+(ll)leftn[i];    for(int i=r-1;i>=0;i--)        ret=ret*10+rightn[i];    return ret;}ll dfs(int l, int r, int cur){    ////////    /*printf("## l=%d r=%d\n",l,r);    for(int i=0;i<l;i++)        putchar('0'+i);    putchar('\n');    for(int i=r-1;i>=0;i--)       putchar('0'+i);    putchar('\n');*/    /////////    ll ans=-1;    if(l+r>lenn)return -1ll;    if(l+r == lenn)    {        ans=cal(l,r);        if(ans>=n)return -1;        return ans;    }    int m= (cur==1) ?num[l]:9;    for(int i=m;i>=0;i--)    {        ///        //printf("*******i=%d m=%d\n",i,m);        ////////        leftn[l]=i;        if( ( l==0 || (l>0&&leftn[l]!=leftn[l-1]) ) && !(l==0 && i==0) && (l+r+1!=lenn) )///        {            for(int k=1;k+l+r<=lenn;k++)///            {                rightn[k+r-1]=i;                ans=max(ans, dfs(l+1,r+k,cur&&(m==i)));            }        }        else        {                ans=max(ans, dfs(l+1, r, cur&&(m==i)));        }        if(ans>0)            return ans;    }    return ans;}int main(){    //IN("H.txt");    int ncase;    scanf("%d",&ncase);    while(ncase--)    {        scanf("%lld",&n);        init();        printf("%lld\n",dfs(0,0,1));    }    return 0;}

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