回答：我的伪在递归方面是模糊的，但这个视频与下面的资源一起很有帮助
http://www.youtube.com/watch?v=p-gpaIGRCQI
对于数独游戏，无法掌握这种回溯递归算法的实现。
我正在尝试使用递归回溯解决数独难题。考虑到我正在处理的问题领域，我仍然无法将通用算法包装在脑海中。
我尝试使用的回溯算法似乎是标准的，但我无法遵循逻辑并知道下面发生了什么。
包括回溯算法及其定义。
编辑：“再次，取出类定义，留下声明并放上伪代码”
这是我利用它的伪代码。
伪代码（C++ 实现）回溯游戏 (81,9) // 表示游戏输入和值的所有可能组合
//All info is loading into a vector of size 81 with the initial state
//puzzle = the initial state 9x9 grid from left to right of integers
vector <int> puzzle
while(!not solved && not the end of the vector){
for(int i =puzzle.begin::iterator i , puzzle.end()) //from 0-80 of the vector until end
if puzzle[i] != 0
//leave alone, original state of board
else
if (valid move) //a guess is allowed in this column/row/square of the board
solution[i] = puzzle_guess[i] //guess a move and insert
else // one of previous guesses were wrong
game.prune(i); //backtracks, or reverses guesses until valid move
}
//游戏初始状态
4 0 0 6 0 5 2 0 3
0 0 0 0 4 9 0 7 5
0 0 0 1 0 7 6 0 0
6 0 1 0 0 0 4 8 7
0 8 0 0 0 0 0 3 0
2 7 4 0 0 0 5 0 6
0 0 8 7 0 3 0 0 0
3 1 0 9 6 0 0 0 0
7 0 9 2 0 8 0 0 1
谢谢
唯一需要知道的线索是声明使用回溯游戏 (81,9) // 表示 81 个可能的数字和 9 表示 9 个不同的选项。
#ifndef BACKTRACK_H
#define BACKTRACK_H
#include <vector>
#include <algorithm>
class BackTrack {
public:
typedef std::vector<unsigned>::const_iterator const_iterator;
typedef std::vector<unsigned>::const_iterator iterator;
BackTrack (unsigned nVariables, unsigned arity=2);
// Create a backtracking state for a problem with
// nVariables variables, each of which has the same
// number of possible values (arity).
template <class Iterator>
BackTrack (Iterator arityBegin,
Iterator arityEnd);
// Create a backtracking state in which each variable may have
// a different number of possible values. The values are obtained
// as integers stored in positions arityBegin .. arityEnd as per
// the usual conventions for C++ iterators. The number of
// variables in the system are inferred from the number of
// positions in the given range.
unsigned operator[] (unsigned variableNumber) const;
// Returns the current value associated with the indicated
// variable.
unsigned numberOfVariables() const;
// Returns the number of variables in the backtracking system.
unsigned arity (unsigned variableNumber) const;
// Returns the number of potential values that can be assigned
// to the indicated variable.
bool more() const;
// Indicates whether additional candidate solutions exist that
// can be reached by subsequent ++ or prune operaations.
void prune (unsigned level);
// Indicates that the combination of values associated with
// variables 0 .. level-1 (inclusive) has been judged unacceptable
// (regardless of the values that could be given to variables
// level..numberOfVariables()-1. The backtracking state will advance
// to the next solution in which at least one of the values in the
// variables 0..level-1 will have changed.
BackTrack& operator++();
// Indicates that the combination of values associated with
// variables 0 .. nVariables-1 (inclusive) has been judged unacceptable.
// The backtracking state will advance
// to the next solution in which at least one of the values in the
// variables 0..level-1 will have changed.
BackTrack operator++(int);
// Same as other operator++, but returns a copy of the old backtrack state
// Iterator operations for easy access to the currently assigned values
const_iterator begin() const {return values.begin();}
iterator begin() {return values.begin();}
const_iterator end() const {return values.end();}
iterator end() {return values.end();}
private:
bool done;
std::vector<unsigned> arities;
std::vector<unsigned> values;
};
inline
unsigned BackTrack::operator[] (unsigned variableNumber) const
// Returns the current value associated with the indicated
// variable.
{
return values[variableNumber];
}
inline
unsigned BackTrack::numberOfVariables() const
// Returns the number of variables in the backtracking system.
{
return values.size();
}
inline
unsigned BackTrack::arity (unsigned variableNumber) const
// Returns the number of potential values that can be assigned
// to the indicated variable.
{
return arities[variableNumber];
}
inline
bool BackTrack::more() const
// Indicates whether additional candidate solutions exist that
// can be reached by subsequent ++ or prune operaations.
{
return !done;
}
template <class Iterator>
BackTrack::BackTrack (Iterator arityBegin,
Iterator arityEnd):
// Create a backtracking state in which each variable may have
// a different number of possible values. The values are obtained
// as integers stored in positions arityBegin .. arityEnd as per
// the usual conventions for C++ iterators. The number of
// variables in the system are inferred from the number of
// positions in the given range.
arities(arityBegin, arityEnd), done(false)
{
fill_n (back_inserter(values), arities.size(), 0);
}
#endif