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feat: add solutions to lc problem: No.0447 #2196

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Jan 8, 2024
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feat: add solutions to lc problem: No.0447 #2196

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189 changes: 136 additions & 53 deletions solution/0400-0499/0447.Number of Boomerangs/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -49,9 +49,13 @@

<!-- 这里可写通用的实现逻辑 -->

计数器实现。
**方法一：枚举 + 计数**

对于每个点，计算其他点到该点的距离，然后按照距离进行分组计数。对每个组中的点进行两两排列组合（A n 取 2，即 `n * (n - 1))`）计数即可。
我们可以枚举 `points` 中的每个点作为回旋镖的点 $i$，然后用一个哈希表 $cnt$ 记录其他点到 $i$ 的距离出现的次数。

如果有 $x$ 个点到 $i$ 的距离相等，那么我们可以任选其中 $2$ 个点作为回旋镖的 $j$ 和 $k$，方案数为 $A_x^2 = x \times (x - 1)$。因此，我们对哈希表中的每个值 $x$，都计算并累加 $A_x^2$，就可以得到满足题目要求的回旋镖数量之和。

时间复杂度 $O(n^2)$，空间复杂度 $O(n)$。其中 $n$ 是数组 `points` 的长度。

<!-- tabs:start -->

Expand All @@ -63,12 +67,25 @@
class Solution:
def numberOfBoomerangs(self, points: List[List[int]]) -> int:
ans = 0
for p in points:
counter = Counter()
for q in points:
distance = (p[0] - q[0]) * (p[0] - q[0]) + (p[1] - q[1]) * (p[1] - q[1])
counter[distance] += 1
ans += sum([val * (val - 1) for val in counter.values()])
for p1 in points:
cnt = Counter()
for p2 in points:
d = dist(p1, p2)
ans += cnt[d]
cnt[d] += 1
return ans << 1
```

```python
class Solution:
def numberOfBoomerangs(self, points: List[List[int]]) -> int:
ans = 0
for p1 in points:
cnt = Counter()
for p2 in points:
d = dist(p1, p2)
cnt[d] += 1
ans += sum(x * (x - 1) for x in cnt.values())
return ans
```

Expand All @@ -80,79 +97,145 @@ class Solution:
class Solution {
public int numberOfBoomerangs(int[][] points) {
int ans = 0;
for (int[] p : points) {
Map<Integer, Integer> counter = new HashMap<>();
for (int[] q : points) {
int distance = (p[0] - q[0]) * (p[0] - q[0]) + (p[1] - q[1]) * (p[1] - q[1]);
counter.put(distance, counter.getOrDefault(distance, 0) + 1);
}
for (int val : counter.values()) {
ans += val * (val - 1);
for (int[] p1 : points) {
Map<Integer, Integer> cnt = new HashMap<>();
for (int[] p2 : points) {
int d = (p1[0] - p2[0]) * (p1[0] - p2[0]) + (p1[1] - p2[1]) * (p1[1] - p2[1]);
ans += cnt.getOrDefault(d, 0);
cnt.merge(d, 1, Integer::sum);
}
}
return ans;
return ans << 1;
}
}
```

### **TypeScript**

```ts
function numberOfBoomerangs(points: number[][]): number {
let ans = 0;
for (let p1 of points) {
let hashMap: Map<number, number> = new Map();
for (let p2 of points) {
const distance = (p1[0] - p2[0]) ** 2 + (p1[1] - p2[1]) ** 2;
hashMap.set(distance, (hashMap.get(distance) || 0) + 1);
}
for (let [, v] of [...hashMap]) {
ans += v * (v - 1);
```java
class Solution {
public int numberOfBoomerangs(int[][] points) {
int ans = 0;
for (int[] p1 : points) {
Map<Integer, Integer> cnt = new HashMap<>();
for (int[] p2 : points) {
int d = (p1[0] - p2[0]) * (p1[0] - p2[0]) + (p1[1] - p2[1]) * (p1[1] - p2[1]);
cnt.merge(d, 1, Integer::sum);
}
for (int x : cnt.values()) {
ans += x * (x - 1);
}
}
return ans;
}
return ans;
}
```

### **Go**
### **C++**

```go
func numberOfBoomerangs(points [][]int) int {
ans := 0
for _, p := range points {
cnt := make(map[int]int)
for _, q := range points {
cnt[(p[0]-q[0])*(p[0]-q[0])+(p[1]-q[1])*(p[1]-q[1])]++
}
for _, v := range cnt {
ans += v * (v - 1)
}
}
return ans
}
```cpp
class Solution {
public:
int numberOfBoomerangs(vector<vector<int>>& points) {
int ans = 0;
for (auto& p1 : points) {
unordered_map<int, int> cnt;
for (auto& p2 : points) {
int d = (p1[0] - p2[0]) * (p1[0] - p2[0]) + (p1[1] - p2[1]) * (p1[1] - p2[1]);
ans += cnt[d];
cnt[d]++;
}
}
return ans << 1;
}
};
```

### **C++**

```cpp
class Solution {
public:
int numberOfBoomerangs(vector<vector<int>>& points) {
int ans = 0;
for (const auto& p : points) {
for (auto& p1 : points) {
unordered_map<int, int> cnt;
for (const auto& q : points) {
++cnt[(p[0] - q[0]) * (p[0] - q[0]) + (p[1] - q[1]) * (p[1] - q[1])];
for (auto& p2 : points) {
int d = (p1[0] - p2[0]) * (p1[0] - p2[0]) + (p1[1] - p2[1]) * (p1[1] - p2[1]);
cnt[d]++;
}
for (const auto& [_, v] : cnt) {
ans += v * (v - 1);
for (auto& [_, x] : cnt) {
ans += x * (x - 1);
}
}
return ans;
}
};
```

### **Go**

```go
func numberOfBoomerangs(points [][]int) (ans int) {
for _, p1 := range points {
cnt := map[int]int{}
for _, p2 := range points {
d := (p1[0]-p2[0])*(p1[0]-p2[0]) + (p1[1]-p2[1])*(p1[1]-p2[1])
ans += cnt[d]
cnt[d]++
}
}
ans <<= 1
return
}
```

```go
func numberOfBoomerangs(points [][]int) (ans int) {
for _, p1 := range points {
cnt := map[int]int{}
for _, p2 := range points {
d := (p1[0]-p2[0])*(p1[0]-p2[0]) + (p1[1]-p2[1])*(p1[1]-p2[1])
cnt[d]++
}
for _, x := range cnt {
ans += x * (x - 1)
}
}
return
}
```

### **TypeScript**

```ts
function numberOfBoomerangs(points: number[][]): number {
let ans = 0;
for (const [x1, y1] of points) {
const cnt: Map<number, number> = new Map();
for (const [x2, y2] of points) {
const d = (x1 - x2) ** 2 + (y1 - y2) ** 2;
ans += cnt.get(d) || 0;
cnt.set(d, (cnt.get(d) || 0) + 1);
}
}
return ans << 1;
}
```

```ts
function numberOfBoomerangs(points: number[][]): number {
let ans = 0;
for (const [x1, y1] of points) {
const cnt: Map<number, number> = new Map();
for (const [x2, y2] of points) {
const d = (x1 - x2) ** 2 + (y1 - y2) ** 2;
cnt.set(d, (cnt.get(d) || 0) + 1);
}
for (const [_, x] of cnt) {
ans += x * (x - 1);
}
}
return ans;
}
```

### **...**

```
Expand Down
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