Panson-Weekly-010
日拱一卒
1 一周见闻
1.1 技术文章
1.2 泛互联网文章
2 技术总结
3 Algorithm(算法题)
class Solution {
public List<Integer> spiralOrder(int[][] matrix) {
List<Integer> ret = new ArrayList<>();
if(matrix.length == 0) {
return ret;
}
int left = 0;
int right = matrix[0].length - 1;
int top = 0;
int bottom = matrix.length - 1;
int index = 0;
while(true) {
for(int i = left; i <= right; i++) {
ret.add(matrix[top][i]);
index++;
}
if(++top > bottom) {
break;
}
for(int i = top; i <= bottom; i++) {
ret.add(matrix[i][right]);
index++;
}
if(left > --right) {
break;
}
for(int i = right; i >= left; i--) {
ret.add(matrix[bottom][i]);
index++;
}
if(--bottom < top) {
break;
}
for(int i = bottom; i >= top; i--) {
ret.add(matrix[i][left]);
index++;
}
if(++left > right) {
break;
}
}
return ret;
}
}
class Solution {
public void rotate(int[][] matrix) {
int n = matrix.length;
for(int i = 0; i < n / 2; i++) {
for(int j = 0; j < n; j++) {
int tmp = matrix[i][j];
matrix[i][j] = matrix[n - i - 1][j];
matrix[n - i - 1][j] = tmp;
}
}
for(int k = 0; k < n; k++) {
for(int l = k + 1; l < n; l++) {
int tmp1 = matrix[k][l];
matrix[k][l] = matrix[l][k];
matrix[l][k] = tmp1;
}
}
}
}
class Solution {
public void setZeroes(int[][] matrix) {
int m = matrix.length;
int n = matrix[0].length;
// 首行标记，默认为 1，表示不置零
int r0 = 1;
// 首列标记，默认为 1，表示不置零
int c0 = 1;
for(int i = 0; i < n; i++) {
if(matrix[0][i] == 0) {
r0 = 0;
break;
}
}
for(int i = 0; i < m; i++) {
if(matrix[i][0] == 0) {
c0 = 0;
break;
}
}
// 将首行首列作为备忘录
for(int i = 1; i < m; i++) {
for(int j = 1; j < n; j++) {
if(matrix[i][j] == 0) {
matrix[i][0] = 0;
matrix[0][j] = 0;
}
}
}
// 遍历第一行，如果有 0，该列置零
for(int j = 1; j < n; j++) {
if(matrix[0][j] == 0) {
// 首行有元素被标记为 1，该列整列被置为 0
for(int i = 0; i < m; i++) {
matrix[i][j] = 0;
}
}
}
// 从第一行开始
for(int i = 1; i < m; i++) {
// 首列有元素被标记为 1， 该行整行被置为 0
if(matrix[i][0] == 0) {
for(int j = 1; j < n; j++) {
matrix[i][j] = 0;
}
}
}
if(r0 == 0) {
for(int i = 0; i < n; i++) {
matrix[0][i] = 0;
}
}
if(c0 == 0) {
for(int i = 0; i < m; i++) {
matrix[i][0] = 0;
}
}
}
}
class Solution {
public boolean canConstruct(String ransomNote, String magazine) {
int[] countMem = new int[26];
for(char c : magazine.toCharArray()) {
countMem[c -'a'] += 1;
}
for(char c1 : ransomNote.toCharArray()) {
if(countMem[c1 - 'a'] <= 0) {
return false;
}
countMem[c1 - 'a'] -= 1;
}
return true;
}
}
class Solution {
public boolean isIsomorphic(String s, String t) {
Map<Character, Character> s2t = new HashMap<>();
Map<Character, Character> t2s = new HashMap<>();
for(int i = 0; i < s.length(); i++) {
char sch = s.charAt(i);
char tch = t.charAt(i);
if(s2t.containsKey(sch) && s2t.get(sch) != tch || t2s.containsKey(tch) && t2s.get(tch) != sch) {
return false;
}
s2t.put(sch, tch);
t2s.put(tch, sch);
}
return true;
}
}
class Solution {
public boolean wordPattern(String pattern, String s) {
String[] split = s.split(" ");
if(pattern.length() != split.length) {
return false;
}
Map<Character, String> a2b = new HashMap<>();
Map<String, Character> b2a = new HashMap<>();
for(int i = 0; i < pattern.length(); i++) {
char ch = pattern.charAt(i);
String str = split[i];
if(a2b.containsKey(ch) && !a2b.get(ch).equals(str) || b2a.containsKey(str) && !b2a.get(str).equals(ch)) {
return false;
}
a2b.put(ch, str);
b2a.put(str, ch);
}
return true;
}
}
class Solution {
public boolean isAnagram(String s, String t) {
int l1 = s.length();
int l2 = t.length();
if(l1 != l2) {
return false;
}
Map<Character, Integer> sCount = new HashMap<>();
Map<Character, Integer> tCount = new HashMap<>();
for(int i = 0; i < l1; i++) {
char sch = s.charAt(i);
char tch = t.charAt(i);
if(sCount.containsKey(sch)) {
sCount.put(s.charAt(i), sCount.get(sch) + 1);
} else {
sCount.put(s.charAt(i), 1);
}
if(tCount.containsKey(t.charAt(i))) {
tCount.put(t.charAt(i), tCount.get(tch) + 1);
} else {
tCount.put(t.charAt(i), 1);
}
}
for(Map.Entry<Character, Integer> entry : sCount.entrySet()) {
if(!entry.getValue().equals(tCount.get(entry.getKey()))) {
return false;
}
}
return true;
}
}
class Solution {
public List<List<String>> groupAnagrams(String[] strs) {
Map<String, List<String>> map = new HashMap<>();
for(String str : strs) {
char[] chs = str.toCharArray();
Arrays.sort(chs);
String strSort = new String(chs);
if(map.containsKey(strSort)) {
map.get(strSort).add(str);
} else {
List<String> arr = new ArrayList<>();
arr.add(str);
map.put(strSort, arr);
}
}
return new ArrayList<>(map.values());
}
}
class Solution {
public int[] twoSum(int[] nums, int target) {
Map<Integer, Integer> map = new HashMap<>();
for(int i = 0; i < nums.length; i++) {
if(map.containsKey(target - nums[i])) {
return new int[]{i, map.get(target - nums[i])};
}
map.put(nums[i], i);
}
return new int[]{-1, -2};
}
}