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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. string change_center(string x, bool bigger)
  5. {
  6. 	int len = x.length();
  7. 	if (len%2==0)
  8. 	{
  9. 		if (bigger)
  10. 		{
  11. 			int index = len/2-1;
  12. 			if(x[index]=='9' and x[abs(index-len)-1]=='9')
  13. 			{
  14. 				while (x[index]=='9' and x[abs(index-len)-1]=='9' and index>0)
  15. 				{
  16. 					x[index] = x[abs(index-len)-1] = '0';
  17. 					--index;
  18. 				}
  19. 				if (x[index]=='9') return "1" + string(len-1, '0') + "1";
  20. 				x[index] = x[abs(index-len)-1] = to_string((x[index]-'0')+1)[0];
  21. 			}
  22. 			else
  23. 			{
  24. 				if (x[len/2-1]>x[len/2]) x[len/2] = x[len/2-1];
  25. 				else x[len/2] = x[len/2-1] = to_string((x[len/2-1]-'0')+1)[0];
  26. 			}
  27. 			return x;
  28. 		}
  29. 		else
  30. 		{
  31. 			if (x[len/2]==x[len/2-1]) return x;
  32. 			else if (x[len/2-1]-'0'>x[len/2]-'0') x[len/2] = x[len/2-1];
  33. 			else x[len/2] = x[len/2-1] = to_string((x[len/2-1]-'0')+1)[0];
  34. 			return x;
  35. 		}
  36. 	}
  37. 	else
  38. 	{
  39. 		if (bigger)
  40. 		{
  41. 			int index = len/2;
  42. 			while(x[index]=='9' and x[abs(index-len)-1]=='9' and index>0)
  43. 			{
  44. 				x[index] = x[abs(index-len)-1] = '0';
  45. 				--index;
  46. 			}
  47. 			if (x[index]=='9') return "1" + string(len-1, '0') + "1";
  48. 			x[index] = x[abs(index-len)-1] = to_string((x[index]-'0')+1)[0];
  49. 		}
  50. 		return x;
  51. 	}
  52. 	return x;
  53. }
  54.  
  55. bool bigger(string a, string b)
  56. {
  57. 	for (int i = 0; i < a.length(); ++i)
  58. 	{
  59. 		if (a[i]-'0'>b[i]-'0') return 1;
  60. 	}
  61. 	return 0;
  62. }
  63.  
  64. string next_pal(string x)
  65. {
  66. 	int len = x.length();
  67. 	string ret;
  68. 	if (len%2==0)
  69. 	{
  70. 		if (len==2)
  71. 		{
  72. 			for (int i = stoi(x)+1; i < stoi(x)*100; ++i)
  73. 			{
  74. 				string y = to_string(i);
  75. 				if (y==string(y.rbegin(), y.rend())) return y;
  76. 			}
  77. 		}
  78. 		string l = string(x.begin(), x.begin()+len/2-1);
  79. 		string r = string(x.begin()+len/2+1, x.end());
  80. 		string l2 = string(l.rbegin(), l.rend());
  81. 		if (bigger(r, l2)) return change_center(l+x[len/2-1]+x[len/2]+l2, 1);
  82. 		else return change_center(l+x[len/2-1]+x[len/2]+l2, 0);
  83. 	}
  84. 	else
  85. 	{
  86. 		if (len==1)
  87. 		{
  88. 			if (x[0]=='9') return "10";
  89. 			else return to_string((x[0]-'0')+1);
  90. 		}
  91. 		string l = string(x.begin(), x.begin()+len/2);
  92. 		string r = string(x.begin()+len/2+1, x.end());
  93. 		string l2 = string(l.rbegin(), l.rend());
  94. 		if (bigger(r, l2)) return change_center(l+x[len/2]+l2, 1);
  95. 		else return change_center(l+x[len/2]+l2, 0);
  96. 	}
  97. 	return x;
  98. }
  99.  
  100. int main()
  101. {
  102. 	ios_base::sync_with_stdio(0);
  103. 	cin.tie(0); cout.tie(0);
  104. 	int t; cin >> t;
  105. 	while (t--)
  106. 	{
  107. 		string x; cin >> x;
  108. 		cout << next_pal(x) << '\n';
  109. 	}
  110. }
Runtime error #stdin #stdout #stderr 0s 15248KB
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Standard input is empty
stdout
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Standard output is empty
stderr
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terminate called after throwing an instance of 'std::length_error'
  what():  basic_string::_M_create
https://ideone.com/NyBFPv
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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