标签：style blog color io os ar strong for 2014
A number that will be the same when it is written forwards or backwards is known as a palindromic number. For example, 1234321 is a palindromic number.
We call a number generalized palindromic number, if after merging all the consecutive same digits, the resulting number is a palindromic number. For example, 122111 is a generalized palindromic number. Because after merging, 122111 turns into 121 which is a palindromic number.
Now you are given a positive integer N, please find the largest generalized palindromic number less than N.
There are multiple test cases. The first line of input contains an integer T (about 5000) indicating the number of test cases. For each test case:
There is only one integer N (1 <= N <= 1018).
For each test case, output the largest generalized palindromic number less than N.
4 12 123 1224 1122
11 121 1221 1121
#include <iostream>
#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;
typedef long long LL;
const int maxn = 20;
int lft[maxn],rgt[maxn];
vector<int> digit;
LL n,ans;
int len;
LL getS(int L,int R) {
LL ret = 0;
for(int i = 0; i < L; i++){
ret *= 10;
ret += lft[i];
}
for(int i = R; i >= 1; i--) {
ret *= 10;
ret += rgt[i];
}
return ret;
}
LL dfs(int L,int R,bool done) {
if(L+R == len) {
LL tmp = getS(L,R);
if(tmp <= n-1) return tmp;
else return 0;
}
int end = done?digit[L]:9;
LL ans = 0;
for(int i = end; i >= 0; i--) {
lft[L] = i;
if(L+R!=len-1&&(L==0||(L>=1&&lft[L]!=lft[L-1]))&&(L!=0||i!=0)){
for(int k = 1; L+R+k <= len-1; k++) {
rgt[k+R] = i;
ans = max(dfs(L+1,R+k,done&&i==end),ans);
}
}else{
ans = max(dfs(L+1,R,done&&i==end),ans);
}
if(ans != 0) return ans;
}
return 0;
}
void init() {
ans = 0;
digit.clear();
scanf("%lld",&n);
LL x = n;
--x;
while(x) {
digit.push_back(x%10);
x /= 10;
}
len = digit.size();
reverse(digit.begin(),digit.end());
}
void solve() {
ans = dfs(0,0,true);
printf("%lld\n",ans);
}
int main() {
int ncase;
cin >> ncase;
while(ncase--) {
init();
solve();
}
return 0;
}
ZOJ3816-Generalized Palindromic Number(DFS数位搜索)
标签：style blog color io os ar strong for 2014
原文地址：http://blog.csdn.net/mowayao/article/details/39205263
