Minor final check performance increase

src/sudoku.cpp

@@ -25,13 +25,19 @@ void Sudoku::FillBoard(std::string filePath) {
 
 // Base global call for solving
 void Sudoku::Solve(void) {
-    _Solve();
+    if (!_Solve()) { std::cerr << "No solution found" << std::endl; }
 }
 
 bool Sudoku::IsBoardSolved(void) {
-    int column, row;
+    int row, column;
-    if (!FindEmptyCell(&column, &row)) { return true; }
+    for (row = 0; row < 9; row += 3) {
-    return false;
+        for (column = 0; column < 9; column += 3) {
+            if (!GetUnusedRow(row).empty()) { return false; }
+            if (!GetUnusedColumn(column).empty()) { return false; }
+            if (!GetUnusedSubgrid(row, column).empty()) { return false; }
+        }
+    }
+    return true;
 }
 
 void Sudoku::Print(void) {
@@ -57,12 +63,19 @@ void Sudoku::RawPrint(void) {
 
 // Recursive call for solving
 bool Sudoku::_Solve(void) {
-    int column, row;
+    int row, column;
-    if (!FindEmptyCell(&column, &row)) { return true; }
+    if (!FindEmptyCell(row, column)) {
-    for (int i : GetUnusedRow(row)) {
+        if (IsBoardSolved()) { return true; }
-        for (int j : GetUnusedColumn(column)) {
+        return false;
-            for (int k : GetUnusedSubgrid(column, row)) {
+    }
-                if (i == j == k) { 
+    std::vector<int> rowPossiblities, columnPossibilities, subgridPossibilities;
+    rowPossiblities = GetUnusedRow(row);
+    columnPossibilities = GetUnusedColumn(column);
+    subgridPossibilities = GetUnusedSubgrid(row, column);
+    for (int i : rowPossiblities) {
+        for (int j : columnPossibilities) {
+            for (int k : subgridPossibilities) {
+                if (i == j && j == k) { 
                     board[row][column] = i; 
                     if (_Solve()) { return true; }
                     board[row][column] = 0;
@@ -70,83 +83,63 @@ bool Sudoku::_Solve(void) {
             }
         }
     }
-    return 0;
+    return false;
 }
 
 // Fills column and row of an empty cell and returns true
 // If no empty cell is found, return false
-bool Sudoku::FindEmptyCell(int* column, int* row) {
+bool Sudoku::FindEmptyCell(int& row, int& column) {
-    for (*row = 0; *row < 9; ++(*row)) {
+    for (row = 0; row < 9; ++(row)) {
-        for (*column = 0; *column < 9; ++(*column)) {
+        for (column = 0; column < 9; ++(column)) {
-            if (board[*row][*column] == 0) { return true; }
+            if (board[row][column] == 0) { return true; }
         }
     }
     return false;
 }
 
-bool Sudoku::IsValidPlacement(int column, int row, int box) {
+// Returns vector of unused numbers in row
-    // Check column and row
+std::vector<int> Sudoku::GetUnusedRow(const int& row) {
-    for (int i = 0; i < 9; ++i) {
+    std::vector<int> leftOver{0,1,2,3,4,5,6,7,8,9};
-        if (board[row][i] == box || board[i][column] == box) {
+    int* box;
-            return false;
+    for (int i = 0; i < 9; i++) {
+        box = &board[row][i];
+        if (leftOver[*box] == *box) { leftOver[*box] = 0; }
     }
+    TrimPossiblities(leftOver);
+    return leftOver;
 }
 
-    // Check subgrid
+// Returns vector of unused numbers in column
-    int startRow = row - row % 3;
+std::vector<int> Sudoku::GetUnusedColumn(const int& column) {
-    int startColumn = column - column % 3;
+    std::vector<int> leftOver{0,1,2,3,4,5,6,7,8,9};
+    int* box;
+    for (int i = 0; i < 9; i++) {
+        box = &board[i][column];
+        if (leftOver[*box] == *box) { leftOver[*box] = 0; }
+    }
+    TrimPossiblities(leftOver);
+    return leftOver;
+}
+
+// Returns vector of unused numbers in subgrid
+std::vector<int> Sudoku::GetUnusedSubgrid(const int& row, const int& column) {
+    std::vector<int> leftOver{0,1,2,3,4,5,6,7,8,9};
+    int* box;
+    int startRow = row - (row % 3);
+    int startColumn = column - (column % 3);
     for (int i = 0; i < 3; ++i) {
         for (int j = 0; j < 3; ++j) {
-            if (board[startRow + i][startColumn + j] == box) { return false; }
+            box = &board[startRow + i][startColumn + j]; 
+            if (leftOver[*box] == *box) { leftOver[*box] = 0; }
         }
     }
-    return true;
+    TrimPossiblities(leftOver);
-}
-
-std::vector<int> Sudoku::GetUnusedRow(int row) {
-    std::vector<int> leftOver{0,1,2,3,4,5,6,7,8,9};
-    int box;
-    for (int i = 0; i < 9; i++) {
-        box = board[row][i];
-        if (leftOver[box] == box) { leftOver[box] = 0; }
-    }
-    for (auto it = leftOver.begin(); it != leftOver.end();) {
-        if (*it == 0) { it = leftOver.erase(it); }
-        else { ++it; }
-    }
     return leftOver;
 }
 
-std::vector<int> Sudoku::GetUnusedColumn(int column) {
+void TrimPossiblities(std::vector<int>& possibilities) {
-    std::vector<int> leftOver{0,1,2,3,4,5,6,7,8,9};
+    for (auto it = possibilities.begin(); it != possibilities.end();) {
-    int box;
+        if (*it == 0) { it = possibilities.erase(it); }
-    for (int i = 0; i < 9; i++) {
-        box = board[i][column];
-        if (leftOver[box] == box) { leftOver[box] = 0; }
-    }
-    for (auto it = leftOver.begin(); it != leftOver.end();) {
-        if (*it == 0) { it = leftOver.erase(it); }
         else { ++it; }
     }
-    return leftOver;
-}
-
-std::vector<int> Sudoku::GetUnusedSubgrid(int column, int row) {
-    std::vector<int> leftOver{0,1,2,3,4,5,6,7,8,9};
-    int box;
-    int startRow = row - row % 3;
-    int startColumn = column - column % 3;
-    for (int i = 0; i < 3; ++i) {
-        for (int j = 0; j < 3; ++j) {
-            box = board[row][column];
-            if (board[startRow + i][startColumn + j] == box) { 
-                leftOver[box] = 0;
-            }
-        }
-    }
-    for (auto it = leftOver.begin(); it != leftOver.end();) {
-        if (*it == 0) { it = leftOver.erase(it); }
-        else { ++it; }
-    }
-    return leftOver;
 }

src/sudoku.hpp

@@ -15,11 +15,12 @@ public:
     void RawPrint(void);
 private:
     bool _Solve(void);
-    bool FindEmptyCell(int* column, int* row);
+    bool FindEmptyCell(int& row, int& column);
-    bool IsValidPlacement(int column, int row, int box);
+    std::vector<int> GetUnusedRow(const int& row);
-    std::vector<int> GetUnusedRow(int row);
+    std::vector<int> GetUnusedColumn(const int& column);
-    std::vector<int> GetUnusedColumn(int column);
+    std::vector<int> GetUnusedSubgrid(const int& row, const int& column);
-    std::vector<int> GetUnusedSubgrid(int column, int row);
 };
 
+void TrimPossiblities(std::vector<int>& possibilities);
+
 #endif

src/sudoku_solver.cpp

@@ -9,6 +9,6 @@ int main(int argc, char* argv[]) {
     Sudoku newGame;
     newGame.FillBoard(argv[1]);
     newGame.Solve();
-    newGame.RawPrint();
+    newGame.Print();
     return 0;
 }