#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
const int Dead=0, Live=1;
const int RowSize=20;
const int GridSize=RowSize * RowSize;
const int numTimes=1000;
const char heavyChar = '#';
const char lightChar = ' ';
void display(int grid[]) {
	int row, col;
	if (RowSize<200) {
	  //	  printf("\012");
	  //sleep(1);
		for (row=0; row<RowSize; ++row) {
			for (col=0; col< RowSize; ++col) {
			  if (grid[row*RowSize+col] == 1)
					printf("%c", heavyChar);
				else 
					printf("%c", lightChar);
			}
			printf("\n");
		}
		printf("=========\n");
	} else {
		// Once I learn X
	}
}

int neighbors(int i, int grid[]) {
  int NW = (i-RowSize-1+GridSize)%GridSize;
  int N = (i-RowSize+GridSize)%GridSize;
  int NE = (i-RowSize+1+GridSize)%GridSize;
  int W = (i-1+GridSize)%GridSize;
  int E = (i+1)%GridSize;
  int SW = (i+RowSize-1)%GridSize;
  int S = (i+RowSize)%GridSize;
  int SE = (i+RowSize+1)%GridSize;

  return 
    grid[NW] + grid[N] + grid[NE] +
    grid[W] + grid[E] +
    grid[SW] +grid[S] + grid[SE];
}

void mkNewGrid(int oldGrid[], int newGrid[]) {
  int i;

  for (i=0; i<GridSize; ++i) {
    int neighborCount = neighbors(i, oldGrid);
    //    printf("i=%d, neighbors=%d\n", i, neighborCount);
    if (oldGrid[i] == Dead) {
      newGrid[i] = (neighborCount == 3) ? Live : Dead;
    } else { // square is alive
      newGrid[i] = ((neighborCount == 2) ||(neighborCount == 3)) ? Live : Dead;
    }
  }
}

int main() {
	int oldGrid[GridSize], newGrid[GridSize];
	int *oldGridP = oldGrid, *newGridP = newGrid;
	int i, row, col;

	// initialize old
	for (row=0; row<RowSize; ++row) {
	  for (col=0; col< RowSize; ++col) {
	    oldGrid[row*RowSize+col] = 0;
	  }
	}
	//	display(oldGrid);
	for (i=0; i<GridSize; i++){
	  //	  printf("%d ", oldGrid[i]);
	}
	printf("\n");
	int offset = 12;
	oldGrid[offset+0] = 1;
	oldGrid[offset+2] = 1;
	oldGrid[offset+RowSize*1+1] = 1;
	oldGrid[offset+RowSize*1+2] = 1;
	oldGrid[offset+RowSize*2+1] = 1;

	for (i=0; i< numTimes; ++i) {
		display(oldGridP);
		sleep(1);
		mkNewGrid(oldGridP, newGridP);
		int* temp = oldGridP;
		oldGridP = newGridP;
		newGridP = temp;

		//		getchar();
		system("clear");
	}
	return 0;
}