73. 矩阵置零
class Solution {
public void setZeroes(int[][] matrix) {
int line = matrix.length;
int col = matrix[0].length;
List<Integer> changeLines = new ArrayList<Integer>();
List<Integer> changeCols = new ArrayList<Integer>();
for(int i = 0; i < line; i++) {
for(int j = 0; j < col; j++) {
if (matrix[i][j] == 0) {
changeLines.add(i);
changeCols.add(j);
}
}
}
for(int i = 0; i < line; i++) {
if (changeLines.contains(i)) {
Arrays.fill(matrix[i], 0);
}
for(int j = 0; j < changeCols.size(); j++) {
matrix[i][changeCols.get(j)] = 0;
}
}
return;
}
}54. 螺旋矩阵
class Solution {
private static final int[][] DIRS = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
public List<Integer> spiralOrder(int[][] matrix) {
int line = matrix.length;
int col = matrix[0].length;
int size = line * col;
List<Integer> ans = new ArrayList<>(line * col);
int i = 0;
int j = -1;
for(int di = 0; ans.size() < size; di = (di + 1) % 4) {
for(int k = 0; k < col; k++) {
i += DIRS[di][0];
j += DIRS[di][1];
ans.add(matrix[i][j]);
}
int tmp = col;
col = line - 1;
line = tmp;
}
return ans;
}
}48. 旋转图像
class Solution {
public void rotate(int[][] matrix) {
int lines = matrix.length;
int cols = matrix[0].length;
int[][] copy = new int[lines][cols];
for(int i = 0; i < lines; i++) {
for(int j = 0; j < cols; j++) {
copy[i][j] = matrix[i][j];
}
}
for(int i = 0; i < lines; i++) {
for(int j = 0; j < cols; j++) {
matrix[j][cols - i - 1] = copy[i][j];
}
}
return;
}
}240. 搜索二维矩阵Ⅱ
class Solution {
public boolean searchMatrix(int[][] matrix, int target) {
int m = matrix.length;
int n = matrix[0].length;
for(int i = 0; i < m; i++) {
if (matrix[i][n - 1] < target) {
continue;
} else if (matrix[i][n - 1] == target) {
return true;
}
for(int j = n - 1; j >= 0; j--) {
if (matrix[i][j] > target) {
continue;
} else if (matrix[i][j] == target) {
return true;
} else {
break;
}
}
}
return false;
}
}