回文数
如果一个数正着读和反着读一样大，则这个数叫做回文数，例如121是回文数，123454321是回文数。
现给定一个正整数x，输出一个回文数y，要求y > x，并且组成x的所有数字之和与组成y的所有数字之和相等，以及y > x。
x在10^1000以内，因为数字较大，我们用字符串作为输入和输出。
如果无解，请输出Impossible。如果有多个y，输出最小的那个。
例如：
输入919，输出14941
输入1，输出Impossible
现给定一个正整数x，输出一个回文数y，要求y > x，并且组成x的所有数字之和与组成y的所有数字之和相等，以及y > x。
x在10^1000以内，因为数字较大，我们用字符串作为输入和输出。
如果无解，请输出Impossible。如果有多个y，输出最小的那个。
例如：
输入919，输出14941
输入1，输出Impossible
#include <stdio.h>
#include <iostream>
#include <string>
using namespace std;
class Test {
public:
static void spreadFromMiddle(int &num, int *buf, int &begin, int &end)
{
while (num)
{
int value = min(9-buf[begin], num/2);
buf[begin] += value;
buf[end] += value;
num -= 2*value;
begin--;
end++;
}
}
static void outputString(int *buf, char *output, int len)
{
int result = 0;
for (int i = 0; i < len; i++)
{
result += buf[i];
output[i] = buf[i] + '0';
}
}
static void arrangeMidOfOddArray(int *buf, int &begin, int &end, int mid, int &num)
{
if (buf[mid] > 9)
{
if (buf[mid] & 1)
{
num += buf[mid] - 9;
buf[mid] = 9;
}
else
{
num += buf[mid] - 8;
buf[mid] = 8;
}
}
begin--;
end++;
}
static string palindrom(string a)
{
int totalNum = 0;
int numOfChar = a.length();
for (int i = 0; i < numOfChar; i++)
{
totalNum += a[i]-'0';
}
if (totalNum < 2 || numOfChar < 2)
{
return "Impossible";
}
int *buf = new int[numOfChar+3];
char *output = new char[numOfChar+3];
memset(buf, 0, (numOfChar+3)*sizeof(int));
memset(output, 0, (numOfChar+3)*sizeof(char));
int begin = 0;
int end = numOfChar-1;
int num = totalNum;
bool success = false;
int len = numOfChar;
bool needExpand = false;
int mid = len/2;
if (!(numOfChar & 1) && (totalNum & 1))
{
needExpand = true;
}
if (!needExpand)
{
while ((begin < end) && (num >= 2*(a[begin]-'0')))
{
buf[begin] = a[begin]-'0';
buf[end] = a[begin] - '0';
num -= 2*(a[begin]-'0');
begin++;
end--;
}
if (begin != end)
{
begin--;
end++;
}
if (begin == end)
{
buf[begin] = num;
num = 0;
for (int i = begin; i < len; i++)
{
if (buf[i] > a[i]-'0')
{
success = true;
break;
}
if (buf[i] < a[i]-'0')
{
break;
}
}
if (success)
{
arrangeMidOfOddArray(buf, begin, end, mid, num);
spreadFromMiddle(num, buf, begin, end);
}
}
}
int newEnd;
if (!success && !needExpand)
{
if (num < 2)
{
int newBegin = begin;
while (newBegin >= 0 && buf[newBegin] == 0)
{
newBegin--;
}
if (newBegin > 0)
{
if (mid == newBegin)
{
num += buf[newBegin];
}
else
{
num += 2*buf[newBegin];
}
buf[newBegin] = 0;
buf[len-1-newBegin] = 0;
}
newEnd = newBegin - 1;
}
else
{
newEnd = begin;
if (begin == end)
{
newEnd = begin-1;
num += buf[mid];
buf[mid] = 0;
}
}
while (newEnd >= 0 && buf[newEnd] == 9)
{
num += 2*buf[newEnd];
buf[newEnd] = 0;
buf[len-1-newEnd] = 0;
newEnd--;
}
if (newEnd >= 0 && num >= 2)
{
buf[newEnd]++;
buf[len-1-newEnd]++;
num -= 2;
if (len & 1)
{
begin = end = mid;
buf[mid] = num;
num = 0;
arrangeMidOfOddArray(buf, begin, end, mid, num);
}
else
{
begin = mid - 1;
end = begin + 1;
}
spreadFromMiddle(num, buf, begin, end);
success = true;
}
}
if (!success)
{
if (totalNum & 1)
{
if (!(numOfChar & 1))
{
len++;
}
else
{
len += 2;
}
}
else
{
len += 1;
}
memset(buf, 0, len*sizeof(int));
buf[0] = buf[len-1] = 1;
num = totalNum - 2;
mid = len/2;
if (len & 1)
{
begin = end = mid;
buf[mid] = num;
num = 0;
arrangeMidOfOddArray(buf, begin, end, mid, num);
}
else
{
begin = mid - 1;
end = begin + 1;
}
spreadFromMiddle(num, buf, begin, end);
success = true;
}
if (success)
{
outputString(buf, output, len);
string result(output);
delete []buf;
delete []output;
return result;
}
else
{
return "Impossible";
}
}
};
//start 提示：自动阅卷起始唯一标识，请勿删除或增加。
int main()
{
cout<<Test::palindrom("131")<<endl;
}
//end //提示：自动阅卷结束唯一标识，请勿删除或增加