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merged 3 commits into from
Jul 11, 2024
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feat: update solutions to lc problems: No.1893,1894 #3257

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abf4049
feat: update solutions to lc problems: No.1893,1894
yanglbme Jul 11, 2024
f9b989b
fix: update
yanglbme Jul 11, 2024
e3f5e9f
fix: update
yanglbme Jul 11, 2024
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62 changes: 32 additions & 30 deletions solution/1800-1899/1893.Check if All the Integers in a Range Are Covered/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -65,13 +65,15 @@ tags:

### 方法一：差分数组

我们可以使用差分数组的思想，对于每个区间 $[l, r]$，我们将 $diff[l]$ 加 $1$，将 $diff[r + 1]$ 减 $1$。
我们可以使用差分数组的思想，创建一个长度为 $52$ 的差分数组 $\textit{diff}$。

最后遍历差分数组，累加每个位置的值，记为 $cur$，如果 $left \le i \le right$ 且 $cur = 0$，则说明 $i$ 没有被任何区间覆盖，返回 `false`。
接下来，我们遍历数组 $\textit{ranges}$，对于每个区间 $[l, r]$，我们令 $\textit{diff}[l]$ 自增 $1$，而 $\textit{diff}[r + 1]$ 自减 $1$。

否则遍历结束后，返回 `true`。
接着，我们遍历差分数组 $\textit{diff}$，维护一个前缀和 $s$，对于每个位置 $i$，我们令 $s$ 自增 $\textit{diff}[i]$，如果 $s \le 0$ 且 $left \le i \le right$，则说明区间 $[left, right]$ 中有一个整数 $i$ 没有被覆盖，返回 $\textit{false}$。

时间复杂度 $O(n + M)$，空间复杂度 $O(M)$。其中 $n$ 和 $M$ 分别为区间的数量和区间的范围。
如果遍历完差分数组 $\textit{diff}$ 后都没有返回 $\textit{false}$，则说明区间 $[left, right]$ 中的每个整数都被 $\textit{ranges}$ 中至少一个区间覆盖，返回 $\textit{true}$。

时间复杂度 $O(n + M)$，空间复杂度 $O(M)$。其中 $n$ 是数组 $\textit{ranges}$ 的长度，而 $M$ 是区间的最大值，本题中 $M \le 50$。

<!-- tabs:start -->

Expand All @@ -84,10 +86,10 @@ class Solution:
for l, r in ranges:
diff[l] += 1
diff[r + 1] -= 1
cur = 0
s = 0
for i, x in enumerate(diff):
cur += x
if left <= i <= right and cur == 0:
s += x
if s <= 0 and left <= i <= right:
return False
return True
```
Expand All @@ -103,10 +105,10 @@ class Solution {
++diff[l];
--diff[r + 1];
}
int cur = 0;
int s = 0;
for (int i = 0; i < diff.length; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur == 0) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand All @@ -121,16 +123,16 @@ class Solution {
class Solution {
public:
bool isCovered(vector<vector<int>>& ranges, int left, int right) {
int diff[52]{};
vector<int> diff(52);
for (auto& range : ranges) {
int l = range[0], r = range[1];
++diff[l];
--diff[r + 1];
}
int cur = 0;
for (int i = 0; i < 52; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur <= 0) {
int s = 0;
for (int i = 0; i < diff.size(); ++i) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand All @@ -144,15 +146,15 @@ public:
```go
func isCovered(ranges [][]int, left int, right int) bool {
diff := [52]int{}
for _, rg := range ranges {
l, r := rg[0], rg[1]
for _, e := range ranges {
l, r := e[0], e[1]
diff[l]++
diff[r+1]--
}
cur := 0
s := 0
for i, x := range diff {
cur += x
if i >= left && i <= right && cur <= 0 {
s += x
if s <= 0 && left <= i && i <= right {
return false
}
}
Expand All @@ -164,15 +166,15 @@ func isCovered(ranges [][]int, left int, right int) bool {

```ts
function isCovered(ranges: number[][], left: number, right: number): boolean {
const diff = new Array(52).fill(0);
const diff: number[] = Array(52).fill(0);
for (const [l, r] of ranges) {
++diff[l];
--diff[r + 1];
}
let cur = 0;
for (let i = 0; i < 52; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur <= 0) {
let s = 0;
for (let i = 0; i < diff.length; ++i) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand All @@ -190,15 +192,15 @@ function isCovered(ranges: number[][], left: number, right: number): boolean {
* @return {boolean}
*/
var isCovered = function (ranges, left, right) {
const diff = new Array(52).fill(0);
const diff = Array(52).fill(0);
for (const [l, r] of ranges) {
++diff[l];
--diff[r + 1];
}
let cur = 0;
for (let i = 0; i < 52; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur <= 0) {
let s = 0;
for (let i = 0; i < diff.length; ++i) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand Down
64 changes: 37 additions & 27 deletions ...on/1800-1899/1893.Check if All the Integers in a Range Are Covered/README_EN.md
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Original file line number Diff line number Diff line change
Expand Up @@ -61,7 +61,17 @@ tags:

<!-- solution:start -->

### Solution 1
### Solution 1: Difference Array

We can use the idea of a difference array to create a difference array $\textit{diff}$ of length $52$.

Next, we iterate through the array $\textit{ranges}$. For each interval $[l, r]$, we increment $\textit{diff}[l]$ by $1$ and decrement $\textit{diff}[r + 1]$ by $1$.

Then, we iterate through the difference array $\textit{diff}$, maintaining a prefix sum $s$. For each position $i$, we increment $s$ by $\textit{diff}[i]$. If $s \le 0$ and $left \le i \le right$, it indicates that an integer $i$ within the interval $[left, right]$ is not covered, and we return $\textit{false}$.

If we finish iterating through the difference array $\textit{diff}$ without returning $\textit{false}$, it means that every integer within the interval $[left, right]$ is covered by at least one interval in $\textit{ranges}$, and we return $\textit{true}$.

The time complexity is $O(n + M)$, and the space complexity is $O(M)$. Here, $n$ is the length of the array $\textit{ranges}$, and $M$ is the maximum value of the interval, which in this case is $M \le 50$.

<!-- tabs:start -->

Expand All @@ -74,10 +84,10 @@ class Solution:
for l, r in ranges:
diff[l] += 1
diff[r + 1] -= 1
cur = 0
s = 0
for i, x in enumerate(diff):
cur += x
if left <= i <= right and cur == 0:
s += x
if s <= 0 and left <= i <= right:
return False
return True
```
Expand All @@ -93,10 +103,10 @@ class Solution {
++diff[l];
--diff[r + 1];
}
int cur = 0;
int s = 0;
for (int i = 0; i < diff.length; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur == 0) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand All @@ -111,16 +121,16 @@ class Solution {
class Solution {
public:
bool isCovered(vector<vector<int>>& ranges, int left, int right) {
int diff[52]{};
vector<int> diff(52);
for (auto& range : ranges) {
int l = range[0], r = range[1];
++diff[l];
--diff[r + 1];
}
int cur = 0;
for (int i = 0; i < 52; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur <= 0) {
int s = 0;
for (int i = 0; i < diff.size(); ++i) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand All @@ -134,15 +144,15 @@ public:
```go
func isCovered(ranges [][]int, left int, right int) bool {
diff := [52]int{}
for _, rg := range ranges {
l, r := rg[0], rg[1]
for _, e := range ranges {
l, r := e[0], e[1]
diff[l]++
diff[r+1]--
}
cur := 0
s := 0
for i, x := range diff {
cur += x
if i >= left && i <= right && cur <= 0 {
s += x
if s <= 0 && left <= i && i <= right {
return false
}
}
Expand All @@ -154,15 +164,15 @@ func isCovered(ranges [][]int, left int, right int) bool {

```ts
function isCovered(ranges: number[][], left: number, right: number): boolean {
const diff = new Array(52).fill(0);
const diff: number[] = Array(52).fill(0);
for (const [l, r] of ranges) {
++diff[l];
--diff[r + 1];
}
let cur = 0;
for (let i = 0; i < 52; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur <= 0) {
let s = 0;
for (let i = 0; i < diff.length; ++i) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand All @@ -180,15 +190,15 @@ function isCovered(ranges: number[][], left: number, right: number): boolean {
* @return {boolean}
*/
var isCovered = function (ranges, left, right) {
const diff = new Array(52).fill(0);
const diff = Array(52).fill(0);
for (const [l, r] of ranges) {
++diff[l];
--diff[r + 1];
}
let cur = 0;
for (let i = 0; i < 52; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur <= 0) {
let s = 0;
for (let i = 0; i < diff.length; ++i) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand Down
10 changes: 5 additions & 5 deletions solution/1800-1899/1893.Check if All the Integers in a Range Are Covered/Solution.cpp
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Open in desktop
Original file line number Diff line number Diff line change
@@ -1,16 +1,16 @@
class Solution {
public:
bool isCovered(vector<vector<int>>& ranges, int left, int right) {
int diff[52]{};
vector<int> diff(52);
for (auto& range : ranges) {
int l = range[0], r = range[1];
++diff[l];
--diff[r + 1];
}
int cur = 0;
for (int i = 0; i < 52; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur <= 0) {
int s = 0;
for (int i = 0; i < diff.size(); ++i) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand Down
10 changes: 5 additions & 5 deletions solution/1800-1899/1893.Check if All the Integers in a Range Are Covered/Solution.go
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,14 +1,14 @@
func isCovered(ranges [][]int, left int, right int) bool {
diff := [52]int{}
for _, rg := range ranges {
l, r := rg[0], rg[1]
for _, e := range ranges {
l, r := e[0], e[1]
diff[l]++
diff[r+1]--
}
cur := 0
s := 0
for i, x := range diff {
cur += x
if i >= left && i <= right && cur <= 0 {
s += x
if s <= 0 && left <= i && i <= right {
return false
}
}
Expand Down
6 changes: 3 additions & 3 deletions solution/1800-1899/1893.Check if All the Integers in a Range Are Covered/Solution.java
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -6,10 +6,10 @@ public boolean isCovered(int[][] ranges, int left, int right) {
++diff[l];
--diff[r + 1];
}
int cur = 0;
int s = 0;
for (int i = 0; i < diff.length; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur == 0) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand Down
10 changes: 5 additions & 5 deletions solution/1800-1899/1893.Check if All the Integers in a Range Are Covered/Solution.js
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -5,15 +5,15 @@
* @return {boolean}
*/
var isCovered = function (ranges, left, right) {
const diff = new Array(52).fill(0);
const diff = Array(52).fill(0);
for (const [l, r] of ranges) {
++diff[l];
--diff[r + 1];
}
let cur = 0;
for (let i = 0; i < 52; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur <= 0) {
let s = 0;
for (let i = 0; i < diff.length; ++i) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand Down
6 changes: 3 additions & 3 deletions solution/1800-1899/1893.Check if All the Integers in a Range Are Covered/Solution.py
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -4,9 +4,9 @@ def isCovered(self, ranges: List[List[int]], left: int, right: int) -> bool:
for l, r in ranges:
diff[l] += 1
diff[r + 1] -= 1
cur = 0
s = 0
for i, x in enumerate(diff):
cur += x
if left <= i <= right and cur == 0:
s += x
if s <= 0 and left <= i <= right:
return False
return True
10 changes: 5 additions & 5 deletions solution/1800-1899/1893.Check if All the Integers in a Range Are Covered/Solution.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,13 +1,13 @@
function isCovered(ranges: number[][], left: number, right: number): boolean {
const diff = new Array(52).fill(0);
const diff: number[] = Array(52).fill(0);
for (const [l, r] of ranges) {
++diff[l];
--diff[r + 1];
}
let cur = 0;
for (let i = 0; i < 52; ++i) {
cur += diff[i];
if (i >= left && i <= right && cur <= 0) {
let s = 0;
for (let i = 0; i < diff.length; ++i) {
s += diff[i];
if (s <= 0 && left <= i && i <= right) {
return false;
}
}
Expand Down
5 changes: 1 addition & 4 deletions solution/1800-1899/1894.Find the Student that Will Replace the Chalk/README.md
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -161,10 +161,7 @@ func chalkReplacer(chalk []int, k int) int {

```ts
function chalkReplacer(chalk: number[], k: number): number {
let s = 0;
for (const x of chalk) {
s += x;
}
const s = chalk.reduce((acc, cur) => acc + cur, 0);
k %= s;
for (let i = 0; ; ++i) {
if (k < chalk[i]) {
Expand Down
5 changes: 1 addition & 4 deletions solution/1800-1899/1894.Find the Student that Will Replace the Chalk/README_EN.md
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Original file line number Diff line number Diff line change
Expand Up @@ -159,10 +159,7 @@ func chalkReplacer(chalk []int, k int) int {

```ts
function chalkReplacer(chalk: number[], k: number): number {
let s = 0;
for (const x of chalk) {
s += x;
}
const s = chalk.reduce((acc, cur) => acc + cur, 0);
k %= s;
for (let i = 0; ; ++i) {
if (k < chalk[i]) {
Expand Down
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