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asahi
2025-05-17 17:01:56 +08:00
parent c4e1e74677
commit a62543b3fd
7 changed files with 454 additions and 0 deletions
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78
20.valid-parentheses.java Normal file
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/*
* @lc app=leetcode id=20 lang=java
*
* [20] Valid Parentheses
*/
// @lc code=start
import java.util.Deque;
class Solution {
public boolean isValid(String s) {
int br_1_cnt = 0, br_2_cnt = 0, br_3_cnt = 0;
Deque<Integer> op_type_stack = new ArrayDeque<Integer>();
for(int i=0;i<s.length();i++) {
char ch = s.charAt(i);
if(isOpenBr(ch)) {
int op_type = getOpenBrType(ch);
op_type_stack.push(op_type);
if(op_type == 1) {
br_1_cnt++;
} else if(op_type == 2) {
br_2_cnt++;
} else if(op_type == 3) {
br_3_cnt++;
}
} else {
int close_type = getCloseBrType(ch);
if(op_type_stack.isEmpty()) {
return false;
} else if(op_type_stack.peek() != close_type) {
return false;
}
op_type_stack.pop();
if(close_type == 1) {
br_1_cnt--;
} else if(close_type == 2) {
br_2_cnt--;
} else if(close_type == 3) {
br_3_cnt--;
}
}
}
return br_1_cnt == 0 && br_2_cnt == 0 && br_3_cnt == 0;
}
private boolean isOpenBr(char ch) {
return ch == '(' || ch == '[' || ch == '{';
}
private int getOpenBrType(char ch) {
switch(ch) {
case '(':
return 1;
case '[':
return 2;
case '{':
return 3;
default:
throw new RuntimeException("invalid open brack");
}
}
private int getCloseBrType(char ch) {
switch(ch) {
case ')':
return 1;
case ']':
return 2;
case '}':
return 3;
default:
throw new RuntimeException("invalid close brack");
}
}
}
// @lc code=end

59
21.merge-two-sorted-lists.java Normal file
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/*
* @lc app=leetcode id=21 lang=java
*
* [21] Merge Two Sorted Lists
*/
// @lc code=start
/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode() {}
* ListNode(int val) { this.val = val; }
* ListNode(int val, ListNode next) { this.val = val; this.next = next; }
* }
*/
class Solution {
public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
if(list1 == null || list2 == null) {
return list1 == null?list2:list1;
}
ListNode h = null, cur = null;
while(list1 != null && list2!=null) {
if(list1.val <= list2.val) {
if(h == null) {
h = cur = list1;
list1 = list1.next;
h.next = null;
} else {
cur.next = list1;
list1 = list1.next;
cur = cur.next;
cur.next = null;
}
} else {
if(h == null) {
h = cur = list2;
list2 = list2.next;
h.next = null;
} else {
cur.next = list2;
list2 = list2.next;
cur = cur.next;
cur.next = null;
}
}
}
if (list1 !=null) {
cur.next = list1;
}
if(list2 != null) {
cur.next = list2;
}
return h;
}
}
// @lc code=end

33
22.generate-parentheses.java Normal file
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/*
* @lc app=leetcode id=22 lang=java
*
* [22] Generate Parentheses
*/
// @lc code=start
class Solution {
public List<String> generateParenthesis(int n) {
List<String> r = new ArrayList<String>();
dfsGenParenthesis(r, "", 0, 0, n);
return r;
}
private void dfsGenParenthesis(List<String> r, String s, int i, int k, int n) {
if(i == n && k == 0) {
r.add(s);
return;
} else if(i > n) {
return;
}
if(i < n) {
String t = s + "(";
dfsGenParenthesis(r, t, i+1, k+1, n);
}
if(k > 0) {
String t = s + ")";
dfsGenParenthesis(r, t, i, k-1, n);
}
}
}
// @lc code=end

24
35.search-insert-position.java Normal file
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/*
* @lc app=leetcode id=35 lang=java
*
* [35] Search Insert Position
*/
// @lc code=start
class Solution {
public int searchInsert(int[] nums, int target) {
int l=0, r = nums.length;
int m;
while(l<r) {
m = l + (r-l)/2;
if(nums[m] >= target) {
r = m;
} else {
l = m + 1;
}
}
return l;
}
}
// @lc code=end

41
45.jump-game-ii.java Normal file
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/*
* @lc app=leetcode id=45 lang=java
*
* [45] Jump Game II
*/
// @lc code=start
class Solution {
public int jump(int[] nums) {
// create array and zset
int[] dp = new int[nums.length];
zset(dp, -1);
dp[0] = 0;
for(int i=0; i<nums.length; i++) {
int w = nums[i];
if(dp[i] < 0) {
// unreachable
continue;
}
for(int j= i+1; j<=i+w && j < nums.length; j++) {
if(dp[j] < 0) {
dp[j] = dp[i] + 1;
} else {
dp[j] = Math.min(dp[j], dp[i] + 1);
}
}
}
return dp[nums.length-1];
}
private void zset(int[] array, int v) {
if(array == null) {
return;
}
for(int i=0;i<array.length; i++) {
array[i] = v;
}
}
}
// @lc code=end

183
51.n-queens.java Normal file
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/*
* @lc app=leetcode id=51 lang=java
*
* [51] N-Queens
*/
// @lc code=start
import java.util.ArrayList;
class Solution {
public List<List<String>> solveNQueens(int n) {
int[][] m = createMap(n);
List<List<String>> r = new ArrayList<>();
dfsNQueen(r, m, 0, n, 0);
return r;
}
private void dfsNQueen(List<List<String>> r, int[][] m, int i, int n, int p) {
if(i == n && pass(m, n, i)) {
r.add(buildRetStr(m));
return;
} else if (i>=n) {
return;
}
if(!pass(m,n, i)) {
return;
}
for(int j = p; j<n*n; j++) {
int x = j / n;
int y = j % n;
if(m[x][y] == 0) {
m[x][y] = 1;
dfsNQueen(r, m, i+1, n, j+1);
m[x][y] = 0;
}
}
}
private boolean pass(int[][] m , int n, int i) {
// todo: check logic
return checkRow(m, n, i) && checkColumn(m, n) && checkLeftSlash(m,n) && checkRightSlash(m,n);
}
private boolean checkRow(int[][] m, int n, int s) {
for(int i=0; i<n; i++) {
if(!checkWithStrategy(m, new Point(i, 0), n, pos->{
return new Point(pos.x, pos.y+1);
})) {
return false;
}
if(i < s && !checkRowNotEmpty(m, n, i)) {
return false;
}
}
return true;
}
private boolean checkRowNotEmpty(int[][] m, int n, int s) {
for(int i=0; i<n; i++) {
if(m[s][i] != 0) {
return true;
}
}
return false;
}
private boolean checkColumn(int[][] m, int n) {
for(int i = 0; i<n; i++) {
if(!checkWithStrategy(m, new Point(0, i), n, pos->{
return new Point(pos.x+1, pos.y);
})) {
return false;
}
}
return true;
}
private boolean checkLeftSlash(int[][] m, int n) {
for(int i = 0; i<n; i++) {
if(!checkWithStrategy(m, new Point(i, 0), n, pos->{
return new Point(pos.x+1, pos.y+1);
})) {
return false;
}
if(!checkWithStrategy(m, new Point(0, i), n, pos->{
return new Point(pos.x+1, pos.y+1);
})) {
return false;
}
}
return true;
}
private boolean checkRightSlash(int[][] m, int n) {
for(int i = 0; i<n; i++) {
if(!checkWithStrategy(m, new Point(0, i), n, pos->{
return new Point(pos.x+1, pos.y-1);
})) {
return false;
}
if(!checkWithStrategy(m, new Point(i, n-1), n, pos->{
return new Point(pos.x+1, pos.y-1);
})) {
return false;
}
}
return true;
}
private boolean checkWithStrategy(int[][] m, Point pos, int n,Function<Point, Point> incrStrategy) {
int c = 0;
if(m[pos.x][pos.y] !=0) {
c++;
}
for(int i=0;i<n-1;i++) {
pos = incrStrategy.apply(pos);
if(pos.x >=n || pos.y>= n || pos.x <0 || pos.y <0) {
break;
}
if(m[pos.x][pos.y] != 0) {
c++;
if(c>1) {
return false;
}
}
}
return true;
}
private int[][] createMap(int n) {
int[][] r = new int[n][n];
zset(r);
return r;
}
private void zset(int[][] m) {
if(m == null) {
return;
}
for (int i = 0; i < m.length; i++) {
if(m[i]==null) {
continue;
}
for(int j = 0; j < m[i].length; j++) {
m[i][j] = 0;
}
}
}
private List<String> buildRetStr(int[][] m) {
List<String> r = new ArrayList<String>();
if(m == null) {
return r;
}
for(int i = 0; i<m.length; i++) {
int[] t = m[i];
if(t == null) {
r.add("");
continue;
}
StringBuilder sbd = new StringBuilder();
for(int j = 0; j<t.length; j++) {
sbd.append(t[j]==0?".":"Q");
}
r.add(sbd.toString());
}
return r;
}
public static class Point {
public int x;
public int y;
public Point(int x, int y) {
this.x = x;
this.y = y;
}
}
}
// @lc code=end

36
77.combinations.java Normal file
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/*
* @lc app=leetcode id=77 lang=java
*
* [77] Combinations
*/
// @lc code=start
class Solution {
public List<List<Integer>> combine(int n, int k) {
List<List<Integer>> r = new ArrayList<List<Integer>>();
List<Integer> rt = new ArrayList<Integer>();
dfsIterate(r,rt, 1, n, k);
return r;
}
private void dfsIterate(List<List<Integer>> r, List<Integer> list, int c, int n, int k) {
if(list.size() == k) {
r.add(shallowCopy(list));
return;
}
if(c > n) {
return;
}
for(int i = c; i<=n; i++) {
List<Integer> p = shallowCopy(list);
p.add(i);
dfsIterate(r, p, i+1, n, k);
}
}
private List<Integer> shallowCopy(List<Integer> list) {
return new ArrayList<>(list);
}
}
// @lc code=end