algorithm-class/公开课/class009/Code01_SetMatrixZeroes.java

package class009;

public class Code01_SetMatrixZeroes {

	/*
	 * 评测代码可以直接去leetcode搜索：Set Matrix Zeroes
	 * 
	 */
	public static void setZeroes1(int[][] matrix) {
		boolean row0Zero = false;
		boolean col0Zero = false;
		int i = 0;
		int j = 0;
		for (i = 0; i < matrix[0].length; i++) {
			if (matrix[0][i] == 0) {
				row0Zero = true;
				break;
			}
		}
		for (i = 0; i < matrix.length; i++) {
			if (matrix[i][0] == 0) {
				col0Zero = true;
				break;
			}
		}
		// 跳过了所有0行、0列的数据
		for (i = 1; i < matrix.length; i++) {
			for (j = 1; j < matrix[0].length; j++) {
				if (matrix[i][j] == 0) {
					matrix[i][0] = 0;
					matrix[0][j] = 0;
				}
			}
		}
		for (i = 1; i < matrix.length; i++) {
			for (j = 1; j < matrix[0].length; j++) {
				if (matrix[i][0] == 0 || matrix[0][j] == 0) {
					matrix[i][j] = 0;
				}
			}
		}
		if (row0Zero) {
			for (i = 0; i < matrix[0].length; i++) {
				matrix[0][i] = 0;
			}
		}
		if (col0Zero) {
			for (i = 0; i < matrix.length; i++) {
				matrix[i][0] = 0;
			}
		}
	}

	public static void setZeroes2(int[][] matrix) {
		boolean col0 = false;
		int i = 0;
		int j = 0;
		for (i = 0; i < matrix.length; i++) {
			for (j = 0; j < matrix[0].length; j++) {
				if (matrix[i][j] == 0) {
					matrix[i][0] = 0;
					if (j == 0) {
						col0 = true;
					} else {
						matrix[0][j] = 0;
					}
				}
			}
		}
		for (i = matrix.length - 1; i >= 0; i--) {
			for (j = 1; j < matrix[0].length; j++) {
				if (matrix[i][0] == 0 || matrix[0][j] == 0) {
					matrix[i][j] = 0;
				}
			}
		}
		if (col0) {
			for (i = 0; i < matrix.length; i++) {
				matrix[i][0] = 0;
			}
		}
	}

}