Hdoj Ztr loves lucky numbers 5676 (DFS emulation)

ZTR loves lucky NumbersTime limit:2000/1000 MS (java/others) Memory limit:65536/65536 K (java/others)
Total submission (s): 918 Accepted Submission (s): 389


Problem Descriptionztr loves lucky numbers. Everybody knows that positive integers is lucky if their decimal representation doesn ' t contain digits other than 4 and 7 . For example, numbers, 744, 4 is lucky and 5, and 467 is not.

Lucky number is super Lucky if it ' s decimal representation contains equal amount of digits 4 and 7. For example, numbers, 7744, 474477 is super lucky and 4, 744, 467 is not.

One day ZTR came across a positive integer n. help him to find the least super lucky number which are not less than N.

Inputthere is T (1≤ n≤ ten 5 )  Cases

For each cases:

The only line contains a positive integer  n(1≤ n≤ ten ) . This number doesn ' t has leading zeroes.

Outputfor each cases
Output the answer
Sample Input

2450047

Sample Output

474747

Sourcebestcoder Round #82 (Div.2) Description of the problem

Ztr likes lucky numbers, he has two requirements for lucky numbers 1: The decimal notation contains only 4, 72: The decimal notation 4 and 7 are equal in number, such as 47,474477, and 4,744,467 is not now ZTR want to know the smallest but not less than n lucky number is what

Enter a description

YesT (1\leq\; T\LEQ\;10^{5})T(1≤T≤1 0? 5  ??)Group data, a positive integer for each set of data nn ，1\leq\;n\leq\;10^{18}1≤N≤1 0?  18   ??

Output description

There is a  t  -line, each line is the answer

Input sample

2450047

Output sample

474747

Hint

Please optimize the algorithm as much as possible, considering the full

Nothing to say, is a DFS simulation, but pay attention to a special sentence, see the code

#include <stdio.h> #include <string.h> #include <algorithm> #include <iostream> #define INF 0x3f3f3f3f#define ll long long#define N 100010using namespace Std;ll a[n];int cnt;void dfs (int l,int r,int len,ll num) {if ( l>len/2| | R>LEN/2) return, if (l+r==len&&l==r) {A[cnt++]=num;return;} if (L<=LEN/2) DFS (L+1,R,LEN,NUM*10+4); if (R<=LEN/2) DFS (l,r+1,len,num*10+7);} int main () {cnt=0;for (int i=2;i<=18;i+=2) DFS (0,0,i,0), int t;ll n;scanf ("%d", &t), while (t--) {scanf ("%lld", &N); if (N>777777777444444444LL)   //Special sentence printf ("44444444447777777777\n"); elseprintf ("%lld\n", A[lower_ Bound (A,a+cnt,n)-A]);} return 0;}

Hdoj Ztr loves lucky numbers 5676 (DFS emulation)