#include <stdio.h>
#include <stdbool.h>
#include <unistd.h>

#define UNDEFINED -1

#define VALUE_TYPE_UNDEFINED UNDEFINED
#define VALUE_TYPE_STATIC 0
#define VALUE_TYPE_GUESS 1

#define COLOR_BLACK 0
#define COLOR_RED 1
#define COLOR_GREEN 2
#define COLOR_YELLOW 3
#define COLOR_BLUE 4
#define COLOR_MAGENTA 5
#define COLOR_CYAN 6
#define COLOR_WHITE 7

#define COLOR_FG 30
#define COLOR_BG 40

struct Value {
	int valueType;
	int value;
};

/*
int sudoku[9][9] = {
	{5, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 1, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 4, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 1, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 2},
	{7, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 3, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 5, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 7, 3, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 6, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, 2, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 6, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 4, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, 9, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 8, 3, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, 8, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 4, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 2},
	{4, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 6, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 7, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 1, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, 9}
};
*/
struct Value sudoku[9][9] = {
	{{VALUE_TYPE_STATIC, 5}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 1}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 4}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 1}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 2}},
	{{VALUE_TYPE_STATIC, 7}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 3}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 5}, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 7}, {VALUE_TYPE_STATIC, 3}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 6}, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 2}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 6}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 4}, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 9}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 8}, {VALUE_TYPE_STATIC, 3}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 8}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 4}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 2}},
	{{VALUE_TYPE_STATIC, 4}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 6}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 7}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}},
	{{VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 1}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_UNDEFINED, UNDEFINED}, {VALUE_TYPE_STATIC, 9}}
};

int calculateRow(int q, int f) { 
	return (q / 3) * 3 + (f / 3);
}

int calculateCol(int q, int f) {
	return (q % 3) * 3 + (f % 3);
}

int calculateQuadrat(int row, int col) {
	return (row / 3) * 3 + col / 3;
}

int calculateField(int row, int col) {
	return (row % 3) * 3 + col % 3;
}

// checks if this value is present anywhere in the row
bool isInRow(int row, int val) {
	for (int col = 0; col < 9; col++) {
		int q = calculateQuadrat(row, col);
		int f = calculateField(row, col);

		if (sudoku[q][f].valueType != VALUE_TYPE_UNDEFINED && sudoku[q][f].value == val) {
			return true;
		}
	}

	return false;
}

// checks if this value is present anywhere in the col
bool isInCol(int col, int val) {
	for (int row = 0; row < 9; row++) {
		int q = calculateQuadrat(row, col);
		int f = calculateField(row, col);

		if (sudoku[q][f].valueType != VALUE_TYPE_UNDEFINED && sudoku[q][f].value == val) {
			return true;
		}
	}

	return false;
}

// checks if this value is present anywhere in the quadrat
bool isInQuadrat(int q, int val) {
	for (int f = 0; f < 9; f++) {
		if (sudoku[q][f].valueType != VALUE_TYPE_UNDEFINED && sudoku[q][f].value == val) {
			return true;
		}
	}

	return false;
}

// check if val is possible value
// i.e. not in row, not in col, not in q
bool check(int q, int f, int val) {
	int row = calculateRow(q, f);
	int col = calculateCol(q, f);

	return !isInRow(row, val)
		&& !isInCol(col, val)
		&& !isInQuadrat(q, val);
}

void printDumpSudoku() {
	printf("\033[H\033[J");
	for (int row = 0; row < 9; row++) {
		if (row % 3 == 0) {
			printf("+-------+-------+-------+\n");
		}
		for (int col = 0; col < 9; col++) {
			if (col % 3 == 0) {
				if (col != 0) {
					printf(" ");
				}
				printf("|");
			}

			int q = calculateQuadrat(row, col);
			int f = calculateField(row, col);
			if (sudoku[q][f].valueType != VALUE_TYPE_UNDEFINED) {
				int color;
				if (sudoku[q][f].valueType == VALUE_TYPE_STATIC) {
					color = COLOR_FG + COLOR_BLUE;
				} else if (sudoku[q][f].valueType == VALUE_TYPE_GUESS) {
					color = COLOR_FG + COLOR_GREEN;
				}
				printf(" \033[%dm%d\033[0m", color, sudoku[q][f].value);
			} else {
				printf(" -");
			}
		}
		printf(" |\n");
	}
	printf("+-------+-------+-------+\n");
}


int main() {
	long iterations = 0;
	long guesses = 0;
	for (int q = 0; q < 9; q++) {
		for (int f = 0; f < 9; f++) {
			if (sudoku[q][f].valueType == VALUE_TYPE_STATIC) {
				continue;
			}

			iterations++;

			// initialize start value
			// might not be 1 if this field was already guessed but we had to go back
			// because the guessed value failed later
			int startVal;
			if (sudoku[q][f].value > UNDEFINED) {
				startVal = sudoku[q][f].value + 1;
			} else {
				startVal = 1;
			}

			// loop through values, if one possible value is found (value is neither in row nor in column)
			// continue to next field
			for (int val = startVal; val <= 9 && sudoku[q][f].valueType == VALUE_TYPE_UNDEFINED; val++) {
				if (check(q, f, val)) {
					sudoku[q][f].valueType = VALUE_TYPE_GUESS;
					sudoku[q][f].value = val;
				}
			}

			// check if a possible value was found
			// if not, go backwards to last guessed value
			if (sudoku[q][f].valueType == VALUE_TYPE_UNDEFINED) {
				// reset value for next time we get back at
				// this position for a guess
				sudoku[q][f].value = UNDEFINED;
				while (sudoku[q][f].valueType != VALUE_TYPE_GUESS) {
					f--;
					if (f < 0) {
						q--;
						if (q < 0) {
							fprintf(stderr, "Error: going backwards made q < 0\n");
							return 1;
						}
						f = 8;
					}
				}
				sudoku[q][f].valueType = VALUE_TYPE_UNDEFINED;
				f--; // next iteration will increment f at beginning (for loop)
			} else {
				// good, possible value found
				//printDumpSudoku();
				//usleep(10 * 1000);
				guesses++;
			}
		}
	}

	printDumpSudoku();
	printf("Iterations: %ld\n", iterations);
	printf("Guesses: %ld\n", guesses);

	return 0;
}