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PM Lee's C++ Sudoku Solver Souce Code.
#include "stdio.h"
int InBlock[81], InRow[81], InCol[81];
const int BLANK = 0;
const int ONES = 0x3fe; // Binary 1111111110
int Entry[81]; // Records entries 1-9 in the grid, as the corresponding bit set to 1
int Block[9], Row[9], Col[9]; // Each int is a 9-bit array
int SeqPtr = 0;
int Sequence[81];
int Count = 0;
int LevelCount[81];
void SwapSeqEntries(int S1, int S2)
{
int temp = Sequence[S2];
Sequence[S2] = Sequence[S1];
Sequence[S1] = temp;
}
void InitEntry(int i, int j, int val)
{
int Square = 9 * i + j;
int valbit = 1 << val;
int SeqPtr2;
// add suitable checks for data consistency
Entry[Square] = valbit;
Block[InBlock[Square]] &= ~valbit;
Col[InCol[Square]] &= ~valbit; // Simpler Col[j] &= ~valbit;
Row[InRow[Square]] &= ~valbit; // Simpler Row[i] &= ~valbit;
SeqPtr2 = SeqPtr;
while (SeqPtr2 < 81 && Sequence[SeqPtr2] != Square)
SeqPtr2++ ;
SwapSeqEntries(SeqPtr, SeqPtr2);
SeqPtr++;
}
void PrintArray()
{
int i, j, valbit, val, Square;
char ch;
Square = 0;
for (i = 0; i < 9; i++) {
if (i % 3 == 0) putc('\n', stdout);
for (j = 0; j < 9; j++) {
if (j % 3 == 0) putc(' ', stdout);
valbit = Entry[Square++];
if (valbit == 0) ch = '-';
else {
for (val = 1; val <= 9; val++)
if (valbit == (1 << val)) {
ch = '0' + val;
break;
}
}
putc(ch,stdout);
}
putc ('\n', stdout);
}
}
void ConsoleInput()
{
int i, j;
char InputString[80];
for (i = 0; i < 9; i++) {
printf("Row[%d] : ", i + 1);
scanf("%s", InputString);
for (j = 0; j < 9; j++) {
char ch = InputString[j];
if (ch >= '1' && ch <= '9')
InitEntry(i, j, ch - '0');
}
}
PrintArray();
}
void PrintStats()
{
int i, j, S;
printf("\nLevel Counts:\n\n");
S = 0;
while (LevelCount[S] == 0) S++;
i = 0;
while (S < 81) {
int Seq = Sequence[S];
printf("(%d, %d):%4d ", Seq / 9 + 1, Seq % 9 + 1, LevelCount[S]);
if (i++ > 4){
printf("\n");
i = 0;
}
S++;
}
printf("\n\nCount = %d\n", Count);
}
void Succeed()
{
PrintArray();
PrintStats();
}
int NextSeq(int S)
{
int S2, Square, Possibles, BitCount;
int T, MinBitCount = 100;
for (T = S; T < 81; T++) {
Square = Sequence[T];
Possibles = Block[InBlock[Square]] & Row[InRow[Square]] & Col[InCol[Square]];
BitCount = 0;
while (Possibles) {
Possibles &= ~(Possibles & -Possibles);
BitCount++;
}
if (BitCount < MinBitCount) {
MinBitCount = BitCount;
S2 = T;
}
}
return S2;
}
void Place(int S)
{
LevelCount[S]++;
Count++;
if (S >= 81) {
Succeed();
return;
}
int S2 = NextSeq(S);
SwapSeqEntries(S, S2);
int Square = Sequence[S];
int BlockIndex = InBlock[Square],
RowIndex = InRow[Square],
ColIndex = InCol[Square];
int Possibles = Block[BlockIndex] & Row[RowIndex] & Col[ColIndex];
while (Possibles) {
int valbit = Possibles & (-Possibles); // Lowest 1 bit in Possibles
Possibles &= ~valbit;
Entry[Square] = valbit;
Block[BlockIndex] &= ~valbit;
Row[RowIndex] &= ~valbit;
Col[ColIndex] &= ~valbit;
Place(S + 1);
Entry[Square] = BLANK; // Could be moved out of the loop
Block[BlockIndex] |= valbit;
Row[RowIndex] |= valbit;
Col[ColIndex] |= valbit;
}
SwapSeqEntries(S, S2);
}
int main(int argc, char* argv[])
{
int i, j, Square;
for (i = 0; i < 9; i++)
for (j = 0; j < 9; j++) {
Square = 9 * i + j;
InRow[Square] = i;
InCol[Square] = j;
InBlock[Square] = (i / 3) * 3 + ( j / 3);
}
for (Square = 0; Square < 81; Square++) {
Sequence[Square] = Square;
Entry[Square] = BLANK;
LevelCount[Square] = 0;
}
for (i = 0; i < 9; i++)
Block[i] = Row[i] = Col[i] = ONES;
ConsoleInput();
Place(SeqPtr);
printf("\n\nTotal Count = %d\n", Count);
return 0;
}
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