Skip to content

feat: add solutions to lc problem: No.2327 #4707

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Sep 8, 2025
Merged

feat: add solutions to lc problem: No.2327 #4707

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
119 changes: 80 additions & 39 deletions solution/2300-2399/2327.Number of People Aware of a Secret/README.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -69,11 +69,13 @@ tags:

### 方法一：差分数组

差分数组 $d[i]$ 记录每天知道秘密的人数变化情况，$cnt[i]$ 记录第 $i$ 天新得知秘密的人数。那么从 $[i+delay,i+forget)$ 的这段时间内，$cnt[i]$ 个人每天都能分享给另外 $cnt[i]$ 个人。
我们用一个差分数组 $d[i]$ 来记录第 $i$ 天知道秘密的人数变化情况，用一个数组 $cnt[i]$ 来记录第 $i$ 天新得知秘密的人数。

最终 $sum(d[:n+1])$ 就是答案。
那么，对于第 $i$ 天新得知秘密的 $cnt[i]$ 个人来说，他们会在 $[i+\text{delay}, i+\text{forget})$ 这段时间内每天都能分享给另外 $cnt[i]$ 个人。

时间复杂度 $O(n^2)$。
答案为 $\sum_{i=1}^{n} d[i]$。

时间复杂度 $O(n^2)$，空间复杂度 $O(n)$。其中 $n$ 为题目给定的整数。

<!-- tabs:start -->

Expand Down Expand Up @@ -102,27 +104,26 @@ class Solution:

```java
class Solution {
private static final int MOD = (int) 1e9 + 7;

public int peopleAwareOfSecret(int n, int delay, int forget) {
final int mod = (int) 1e9 + 7;
int m = (n << 1) + 10;
long[] d = new long[m];
long[] cnt = new long[m];
cnt[1] = 1;
for (int i = 1; i <= n; ++i) {
if (cnt[i] > 0) {
d[i] = (d[i] + cnt[i]) % MOD;
d[i + forget] = (d[i + forget] - cnt[i] + MOD) % MOD;
d[i] = (d[i] + cnt[i]) % mod;
d[i + forget] = (d[i + forget] - cnt[i] + mod) % mod;
int nxt = i + delay;
while (nxt < i + forget) {
cnt[nxt] = (cnt[nxt] + cnt[i]) % MOD;
cnt[nxt] = (cnt[nxt] + cnt[i]) % mod;
++nxt;
}
}
}
long ans = 0;
for (int i = 1; i <= n; ++i) {
ans = (ans + d[i]) % MOD;
ans = (ans + d[i]) % mod;
}
return (int) ans;
}
Expand All @@ -132,29 +133,29 @@ class Solution {
#### C++

```cpp
using ll = long long;
const int mod = 1e9 + 7;

class Solution {
public:
int peopleAwareOfSecret(int n, int delay, int forget) {
const int mod = 1e9 + 7;
int m = (n << 1) + 10;
vector<ll> d(m);
vector<ll> cnt(m);
vector<long long> d(m), cnt(m);
cnt[1] = 1;
for (int i = 1; i <= n; ++i) {
if (!cnt[i]) continue;
d[i] = (d[i] + cnt[i]) % mod;
d[i + forget] = (d[i + forget] - cnt[i] + mod) % mod;
int nxt = i + delay;
while (nxt < i + forget) {
cnt[nxt] = (cnt[nxt] + cnt[i]) % mod;
++nxt;
for (int i = 1; i <= n; i++) {
if (cnt[i]) {
d[i] = (d[i] + cnt[i]) % mod;
d[i + forget] = (d[i + forget] - cnt[i] + mod) % mod;
int nxt = i + delay;
while (nxt < i + forget) {
cnt[nxt] = (cnt[nxt] + cnt[i]) % mod;
nxt++;
}
}
}
int ans = 0;
for (int i = 1; i <= n; ++i) ans = (ans + d[i]) % mod;
return ans;
long long ans = 0;
for (int i = 0; i <= n; i++) {
ans += d[i];
}
return ans % mod;
}
};
```
Expand Down Expand Up @@ -192,25 +193,65 @@ func peopleAwareOfSecret(n int, delay int, forget int) int {

```ts
function peopleAwareOfSecret(n: number, delay: number, forget: number): number {
let dp = new Array(n + 1).fill(0n);
dp[1] = 1n;
for (let i = 2; i <= n; i++) {
let pre = 0n;
for (let j = i - forget + 1; j <= i - delay; j++) {
if (j > 0) {
pre += dp[j];
const mod = 1e9 + 7;
const m = (n << 1) + 10;
const d: number[] = Array(m).fill(0);
const cnt: number[] = Array(m).fill(0);

cnt[1] = 1;
for (let i = 1; i <= n; ++i) {
if (cnt[i] > 0) {
d[i] = (d[i] + cnt[i]) % mod;
d[i + forget] = (d[i + forget] - cnt[i] + mod) % mod;
let nxt = i + delay;
while (nxt < i + forget) {
cnt[nxt] = (cnt[nxt] + cnt[i]) % mod;
++nxt;
}
}
dp[i] = pre;
}
let pre = 0n;
let i = n + 1;
for (let j = i - forget; j < i; j++) {
if (j > 0) {
pre += dp[j];

let ans = 0;
for (let i = 1; i <= n; ++i) {
ans = (ans + d[i]) % mod;
}
return ans;
}
```

#### Rust

```rust
impl Solution {
pub fn people_aware_of_secret(n: i32, delay: i32, forget: i32) -> i32 {
let n = n as usize;
let delay = delay as usize;
let forget = forget as usize;
let m = (n << 1) + 10;
let modulo: i64 = 1_000_000_007;

let mut d = vec![0i64; m];
let mut cnt = vec![0i64; m];

cnt[1] = 1;
for i in 1..=n {
if cnt[i] > 0 {
d[i] = (d[i] + cnt[i]) % modulo;
d[i + forget] = (d[i + forget] - cnt[i] + modulo) % modulo;
let mut nxt = i + delay;
while nxt < i + forget {
cnt[nxt] = (cnt[nxt] + cnt[i]) % modulo;
nxt += 1;
}
}
}

let mut ans: i64 = 0;
for i in 1..=n {
ans = (ans + d[i]) % modulo;
}
ans as i32
}
return Number(pre % BigInt(10 ** 9 + 7));
}
```

Expand Down
121 changes: 84 additions & 37 deletions solution/2300-2399/2327.Number of People Aware of a Secret/README_EN.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -67,7 +67,15 @@ Day 4: A forgets the secret. B, C, and D share the secret with 3 new people. (6

<!-- solution:start -->

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

We use a difference array $d[i]$ to record the change in the number of people who know the secret on day $i$, and an array $cnt[i]$ to record the number of people who newly learn the secret on day $i$.

For the $cnt[i]$ people who newly learn the secret on day $i$, they can share the secret with another $cnt[i]$ people each day during the interval $[i+\text{delay}, i+\text{forget})$.

The answer is $\sum_{i=1}^{n} d[i]$.

The time complexity is $O(n^2)$, and the space complexity is $O(n)$, where $n$ is the given integer.

<!-- tabs:start -->

Expand Down Expand Up @@ -96,27 +104,26 @@ class Solution:

```java
class Solution {
private static final int MOD = (int) 1e9 + 7;

public int peopleAwareOfSecret(int n, int delay, int forget) {
final int mod = (int) 1e9 + 7;
int m = (n << 1) + 10;
long[] d = new long[m];
long[] cnt = new long[m];
cnt[1] = 1;
for (int i = 1; i <= n; ++i) {
if (cnt[i] > 0) {
d[i] = (d[i] + cnt[i]) % MOD;
d[i + forget] = (d[i + forget] - cnt[i] + MOD) % MOD;
d[i] = (d[i] + cnt[i]) % mod;
d[i + forget] = (d[i + forget] - cnt[i] + mod) % mod;
int nxt = i + delay;
while (nxt < i + forget) {
cnt[nxt] = (cnt[nxt] + cnt[i]) % MOD;
cnt[nxt] = (cnt[nxt] + cnt[i]) % mod;
++nxt;
}
}
}
long ans = 0;
for (int i = 1; i <= n; ++i) {
ans = (ans + d[i]) % MOD;
ans = (ans + d[i]) % mod;
}
return (int) ans;
}
Expand All @@ -126,29 +133,29 @@ class Solution {
#### C++

```cpp
using ll = long long;
const int mod = 1e9 + 7;

class Solution {
public:
int peopleAwareOfSecret(int n, int delay, int forget) {
const int mod = 1e9 + 7;
int m = (n << 1) + 10;
vector<ll> d(m);
vector<ll> cnt(m);
vector<long long> d(m), cnt(m);
cnt[1] = 1;
for (int i = 1; i <= n; ++i) {
if (!cnt[i]) continue;
d[i] = (d[i] + cnt[i]) % mod;
d[i + forget] = (d[i + forget] - cnt[i] + mod) % mod;
int nxt = i + delay;
while (nxt < i + forget) {
cnt[nxt] = (cnt[nxt] + cnt[i]) % mod;
++nxt;
for (int i = 1; i <= n; i++) {
if (cnt[i]) {
d[i] = (d[i] + cnt[i]) % mod;
d[i + forget] = (d[i + forget] - cnt[i] + mod) % mod;
int nxt = i + delay;
while (nxt < i + forget) {
cnt[nxt] = (cnt[nxt] + cnt[i]) % mod;
nxt++;
}
}
}
int ans = 0;
for (int i = 1; i <= n; ++i) ans = (ans + d[i]) % mod;
return ans;
long long ans = 0;
for (int i = 0; i <= n; i++) {
ans += d[i];
}
return ans % mod;
}
};
```
Expand Down Expand Up @@ -186,25 +193,65 @@ func peopleAwareOfSecret(n int, delay int, forget int) int {

```ts
function peopleAwareOfSecret(n: number, delay: number, forget: number): number {
let dp = new Array(n + 1).fill(0n);
dp[1] = 1n;
for (let i = 2; i <= n; i++) {
let pre = 0n;
for (let j = i - forget + 1; j <= i - delay; j++) {
if (j > 0) {
pre += dp[j];
const mod = 1e9 + 7;
const m = (n << 1) + 10;
const d: number[] = Array(m).fill(0);
const cnt: number[] = Array(m).fill(0);

cnt[1] = 1;
for (let i = 1; i <= n; ++i) {
if (cnt[i] > 0) {
d[i] = (d[i] + cnt[i]) % mod;
d[i + forget] = (d[i + forget] - cnt[i] + mod) % mod;
let nxt = i + delay;
while (nxt < i + forget) {
cnt[nxt] = (cnt[nxt] + cnt[i]) % mod;
++nxt;
}
}
dp[i] = pre;
}
let pre = 0n;
let i = n + 1;
for (let j = i - forget; j < i; j++) {
if (j > 0) {
pre += dp[j];

let ans = 0;
for (let i = 1; i <= n; ++i) {
ans = (ans + d[i]) % mod;
}
return ans;
}
```

#### Rust

```rust
impl Solution {
pub fn people_aware_of_secret(n: i32, delay: i32, forget: i32) -> i32 {
let n = n as usize;
let delay = delay as usize;
let forget = forget as usize;
let m = (n << 1) + 10;
let modulo: i64 = 1_000_000_007;

let mut d = vec![0i64; m];
let mut cnt = vec![0i64; m];

cnt[1] = 1;
for i in 1..=n {
if cnt[i] > 0 {
d[i] = (d[i] + cnt[i]) % modulo;
d[i + forget] = (d[i + forget] - cnt[i] + modulo) % modulo;
let mut nxt = i + delay;
while nxt < i + forget {
cnt[nxt] = (cnt[nxt] + cnt[i]) % modulo;
nxt += 1;
}
}
}

let mut ans: i64 = 0;
for i in 1..=n {
ans = (ans + d[i]) % modulo;
}
ans as i32
}
return Number(pre % BigInt(10 ** 9 + 7));
}
```

Expand Down
34 changes: 17 additions & 17 deletions solution/2300-2399/2327.Number of People Aware of a Secret/Solution.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,25 +1,25 @@
using ll = long long;
const int mod = 1e9 + 7;

class Solution {
public:
int peopleAwareOfSecret(int n, int delay, int forget) {
const int mod = 1e9 + 7;
int m = (n << 1) + 10;
vector<ll> d(m);
vector<ll> cnt(m);
vector<long long> d(m), cnt(m);
cnt[1] = 1;
for (int i = 1; i <= n; ++i) {
if (!cnt[i]) continue;
d[i] = (d[i] + cnt[i]) % mod;
d[i + forget] = (d[i + forget] - cnt[i] + mod) % mod;
int nxt = i + delay;
while (nxt < i + forget) {
cnt[nxt] = (cnt[nxt] + cnt[i]) % mod;
++nxt;
for (int i = 1; i <= n; i++) {
if (cnt[i]) {
d[i] = (d[i] + cnt[i]) % mod;
d[i + forget] = (d[i + forget] - cnt[i] + mod) % mod;
int nxt = i + delay;
while (nxt < i + forget) {
cnt[nxt] = (cnt[nxt] + cnt[i]) % mod;
nxt++;
}
}
}
int ans = 0;
for (int i = 1; i <= n; ++i) ans = (ans + d[i]) % mod;
return ans;
long long ans = 0;
for (int i = 0; i <= n; i++) {
ans += d[i];
}
return ans % mod;
}
};
};
Loading