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feat: add solutions to lc problems: No.3180,3181 #3094

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Original file line number Diff line number Diff line change
Expand Up @@ -222,4 +222,240 @@ function maxTotalReward(rewardValues: number[]): number {

<!-- solution:end -->

<!-- solution:start -->

### 方法二:动态规划

我们定义 $f[i][j]$ 表示用前 $i$ 个奖励值,能否得到总奖励 $j$。初始时 $f[0][0] = \text{True}$,其余值均为 $\text{False}$。

我们考虑第 $i$ 个奖励值 $v$,如果我们不选择它,那么 $f[i][j] = f[i - 1][j]$;如果我们选择它,那么 $f[i][j] = f[i - 1][j - v]$,其中 $0 \leq j - v \lt v$。即状态转移方程为:

$$
f[i][j] = f[i - 1][j] \vee f[i - 1][j - v]
$$

最终答案为 $\max\{j \mid f[n][j] = \text{True}\}$。

由于 $f[i][j]$ 只与 $f[i - 1][j]$ 和 $f[i - 1][j - v]$ 有关,我们可以优化掉第一维,只使用一个一维数组进行状态转移。

时间复杂度 $O(n \times M)$,空间复杂度 $O(M)$。其中 $n$ 是数组 `rewardValues` 的长度,而 $M$ 是数组 `rewardValues` 中的最大值的两倍。

<!-- tabs:start -->

#### Python3

```python
class Solution:
def maxTotalReward(self, rewardValues: List[int]) -> int:
nums = sorted(set(rewardValues))
m = nums[-1] << 1
f = [False] * m
f[0] = True
for v in nums:
for j in range(m):
if 0 <= j - v < v:
f[j] |= f[j - v]
ans = m - 1
while not f[ans]:
ans -= 1
return ans
```

#### Java

```java
class Solution {
public int maxTotalReward(int[] rewardValues) {
int[] nums = Arrays.stream(rewardValues).distinct().sorted().toArray();
int n = nums.length;
int m = nums[n - 1] << 1;
boolean[] f = new boolean[m];
f[0] = true;
for (int v : nums) {
for (int j = 0; j < m; ++j) {
if (0 <= j - v && j - v < v) {
f[j] |= f[j - v];
}
}
}
int ans = m - 1;
while (!f[ans]) {
--ans;
}
return ans;
}
}
```

#### C++

```cpp
class Solution {
public:
int maxTotalReward(vector<int>& rewardValues) {
sort(rewardValues.begin(), rewardValues.end());
rewardValues.erase(unique(rewardValues.begin(), rewardValues.end()), rewardValues.end());
int n = rewardValues.size();
int m = rewardValues.back() << 1;
bool f[m];
memset(f, false, sizeof(f));
f[0] = true;
for (int v : rewardValues) {
for (int j = 1; j < m; ++j) {
if (0 <= j - v && j - v < v) {
f[j] = f[j] || f[j - v];
}
}
}
int ans = m - 1;
while (!f[ans]) {
--ans;
}
return ans;
}
};
```
#### Go
```go
func maxTotalReward(rewardValues []int) int {
slices.Sort(rewardValues)
nums := slices.Compact(rewardValues)
n := len(nums)
m := nums[n-1] << 1
f := make([]bool, m)
f[0] = true
for _, v := range nums {
for j := 1; j < m; j++ {
if 0 <= j-v && j-v < v {
f[j] = f[j] || f[j-v]
}
}
}
ans := m - 1
for !f[ans] {
ans--
}
return ans
}
```

#### TypeScript

```ts
function maxTotalReward(rewardValues: number[]): number {
const nums = Array.from(new Set(rewardValues)).sort((a, b) => a - b);
const n = nums.length;
const m = nums[n - 1] << 1;
const f: boolean[] = Array(m).fill(false);
f[0] = true;
for (const v of nums) {
for (let j = 1; j < m; ++j) {
if (0 <= j - v && j - v < v) {
f[j] = f[j] || f[j - v];
}
}
}
let ans = m - 1;
while (!f[ans]) {
--ans;
}
return ans;
}
```

<!-- tabs:end -->

<!-- solution:end -->

<!-- solution:start -->

### 方法三:动态规划 + 位运算

我们可以对方法二进行优化,定义一个二进制数 $f$ 保存当前的状态,其中 $f$ 的第 $i$ 位为 $1$ 表示当前总奖励为 $i$ 是可达的。

观察方法二的状态转移方程 $f[j] = f[j] \vee f[j - v]$,这相当于取 $f$ 的低 $v$ 位,再左移 $v$ 位,然后与原来的 $f$ 进行或运算。

那么答案为 $f$ 的最高位的位置。

时间复杂度 $O(n \times M / w)$,空间复杂度 $O(n + M / w)$。其中 $n$ 是数组 `rewardValues` 的长度,而 $M$ 是数组 `rewardValues` 中的最大值的两倍。整数 $w = 32$ 或 $64$。

<!-- tabs:start -->

#### Python3

```python
class Solution:
def maxTotalReward(self, rewardValues: List[int]) -> int:
nums = sorted(set(rewardValues))
f = 1
for v in nums:
f |= (f & ((1 << v) - 1)) << v
return f.bit_length() - 1
```

#### Java

```java
import java.math.BigInteger;
import java.util.Arrays;

class Solution {
public int maxTotalReward(int[] rewardValues) {
int[] nums = Arrays.stream(rewardValues).distinct().sorted().toArray();
BigInteger f = BigInteger.ONE;
for (int v : nums) {
BigInteger mask = BigInteger.ONE.shiftLeft(v).subtract(BigInteger.ONE);
BigInteger shifted = f.and(mask).shiftLeft(v);
f = f.or(shifted);
}
return f.bitLength() - 1;
}
}
```

#### C++

```cpp
class Solution {
public:
int maxTotalReward(vector<int>& rewardValues) {
sort(rewardValues.begin(), rewardValues.end());
rewardValues.erase(unique(rewardValues.begin(), rewardValues.end()), rewardValues.end());
bitset<100000> f{1};
for (int v : rewardValues) {
int shift = f.size() - v;
f |= f << shift >> (shift - v);
}
for (int i = rewardValues.back() * 2 - 1;; i--) {
if (f.test(i)) {
return i;
}
}
}
};
```
#### Go
```go
func maxTotalReward(rewardValues []int) int {
slices.Sort(rewardValues)
rewardValues = slices.Compact(rewardValues)
one := big.NewInt(1)
f := big.NewInt(1)
p := new(big.Int)
for _, v := range rewardValues {
mask := p.Sub(p.Lsh(one, uint(v)), one)
f.Or(f, p.Lsh(p.And(f, mask), uint(v)))
}
return f.BitLen() - 1
}
```

<!-- tabs:end -->

<!-- solution:end -->

<!-- problem:end -->
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