题目链接:http://www.spoj.com/problems/BALNUM/en/ Time limit: 0.123s Source limit: 50000B Memory limit: 1536MB Balanced numbers have been used by mathematicians for centuries. A positive integer is considered a balanced number if: 1)      Every even digit…

Balanced Numbers Balanced numbers have been used by mathematicians for centuries. A positive integer is considered a balanced number if: 1)      Every even digit appears an odd number of times in its decimal representation 2)      Every odd digit app…

链接: https://vjudge.net/problem/SPOJ-BALNUM 题意: Balanced numbers have been used by mathematicians for centuries. A positive integer is considered a balanced number if: 1) Every even digit appears an odd number of times in its decimal representation 2)…

题目:http://www.spoj.com/problems/BALNUM/en/ 题意:找出区间[A, B]内所有奇数字出现次数为偶数,偶数字出现次数为计数的数的个数. 分析: 明显的数位dp题,首先,只有3种状态(0:没出现过, 1:数字出现奇数次, 2:数字出现偶数次),所以, 0~9 出现的次数就可以用3进制表示,最大的数就是 310 ,那么我们就可以把1019 哈希到310 内了.其中,我们可以假设: (0:30  ,1:31 , 2:32 , .... , 9: 39 ) 当第一次…

思路: 把0~9的状态用3进制表示,数据量3^10 代码: #include<cstdio> #include<map> #include<set> #include<queue> #include<cstring> #include<string> #include<cmath> #include<cstdlib> #include<iostream> #include<algorithm&…

题意: 求出所给范围内满足其数位上的奇数出现偶数次,数位上的偶数出现奇数次(或不出现)的数的个数. 思路: 对于0 ~ 9 每个数有3种情况. 1.没出现过 2.出现奇数次 3.出现偶数次 那么就可以用三进制来表示状态. #include <iostream> #include <cstring> #include <cstdio> #include <cmath> using namespace std; typedef long long ll; ; i…

题意: 平衡树定义为“一个整数的某个数位若是奇数,则该奇数必定出现偶数次:偶数位则必须出现奇数次”,比如 222,数位为偶数2,共出现3次,是奇数次,所以合法.给一个区间[L,R],问有多少个平衡数? 思路: 这题比较好解决,只有前导零问题需要解决.如果枚举到011,那么其前导零(偶数)出现了1次而已,而此数11却是平衡数,所以不允许前导零的出现! 由于dfs时必定会枚举到前导零,否则位数较少的那些统计不到.状态需要3维or2维也行,3维的比较容易处理,用一维表示数位出现次数,另一维表示数位是否…

BALNUM - Balanced Numbers Time limit:123 ms Memory limit:1572864 kB Balanced numbers have been used by mathematicians for centuries. A positive integer is considered a balanced number if: 1)      Every even digit appears an odd number of times in its…

Balanced numbers have been used by mathematicians for centuries. A positive integer is considered a balanced number if: 1)      Every even digit appears an odd number of times in its decimal representation 2)      Every odd digit appears an even numb…

题目链接:http://www.spoj.com/problems/BALNUM/en/ 题意:问你在[A,B]的闭区间内有几个满足要求的数,要求为每个出现的奇数个数为偶数个,每个出现的偶数个数为奇数个. 显然dfs很好想到dfs(int len , int even[] , int odd[] , int flag , int first) even表示前len位出现偶数的总状态 , odd表示前len位出现奇数的总状态,first表示是否为首位(特判全为0的结果) 但是这样写dfs dp不好…