螺旋矩陣

#include <iostream>
using namespace std;

#define M 4
#define N 5

void init(int* arr, int m, int n) {
	for (int i = 1; i <= m * n; ++i) {
		arr[i - 1] = i;
	}
}
//定義四個方向的界限,不夠優化
int* spiralMatrix(int matrix[M][N], int m, int n) {
	int* trace = new int[m * n];
	int step = 0;
	int left = 0;
	int right = n - 1;
	int up = m - 1;
	int down = 1;

	int direct = 1;
	while (true) {
		if (direct == 1) {
			for (int i = left; i <= right; ++i) {
				trace[step++] = matrix[down - 1][i];
			}
			left++;
			direct++;
		} else if (direct == 2) {
			for (int i = down; i <= up; ++i) {
				trace[step++] = matrix[i][right];
			}
			down++;
			direct++;
		} else if (direct == 3) {
			for (int i = right - 1; i >= left - 1; --i) {
				trace[step++] = matrix[up][i];
			}
			right--;
			direct++;
		} else {
			for (int i = up - 1; i >= down - 1; --i) {
				trace[step++] = matrix[i][left - 1];
			}
			up--;
			direct = 1;
		}
		if (step == m * n)
			break;
	}
	return trace;
}

/*
 * 優解:考慮每一圈起始點的規律(start,start)
 * 只考慮起始座標和x,y上的界限關係,省去2個界限start*2<cols&&start*2<rows
 * 規律更加清晰
 */
int* spiralMatrix2(int matrix[M][N], int rows, int cols) {
	int* trace = new int[rows * cols];
	int step = 0;
	int start = 0;
	int endX = cols - 1 - start;
	int endY = rows - 1 - start;
	while (start * 2 < rows && start * 2 < cols) {
		//向右：至少有一格,即start<=endX
		for (int i = start; i <= endX; ++i) {
			trace[step++] = matrix[start][i];
		}
		//向下：至少2行,即start<endY
		if (start < endY) {
			for (int i = start + 1; i <= endY; ++i) {
				trace[step++] = matrix[i][endX];
			}
		}
		//向左：至少2行且至少2列,即start<endY&&start<endX
		if (start < endX && start < endY) {
			for (int i = endX - 1; i >= start; --i) {
				trace[step++] = matrix[endY][i];
			}
		}
		//向上：至少3行且至少2列,即start<endY-1&&start<endX
		if (start < endX && start < endY - 1) {
			for (int i = endY - 1; i >= start + 1; --i) {
				trace[step++] = matrix[i][start];
			}
		}
		start++;
		endX = cols - 1 - start;
		endY = rows - 1 - start;
	}
	return trace;
}

int main() {
	int matrix[M][N] = { 0 };
	init(matrix[0], M, N);

	int* trace1 = spiralMatrix(matrix, M, N);
	int* trace2 = spiralMatrix2(matrix, M, N);
	for (int i = 0; i < M * N; ++i) {
		cout << trace1[i] << " ";
	}
	cout << endl;
	for (int i = 0; i < M * N; ++i) {
		cout << trace2[i] << " ";
	}
	return 0;
}