feat: add solutions to lc problem: No.2251 (doocs#1334)

No.2251.Number of Flowers in Full Bloom

Author: yanglbme

solution/2200-2299/2251.Number of Flowers in Full Bloom/README.md

@@ -48,14 +48,17 @@
 
 <!-- 这里可写通用的实现逻辑 -->
 
-离散差分+离散查询
+**方法一：排序 + 二分查找**
 
--   按开始时间对鲜花进行排序
--   按结束时间对鲜花进行排序
--   在每个人的新花数组中执行二分搜索
--   对按开始时间排序的花进行分析，`bisect_right` 给出给定人员考虑的最后一朵花
--   对按结束时间排序的花执行 `flowers` 操作`bisect_left`，给出针对给定人员考虑的第一朵花
--   两者相减，就得到当时盛开的花朵
+我们将花按照开始时间和结束时间分别排序，然后对于每个人，我们可以使用二分查找来找到他们到达时在花期内花的数目。就是说，找出在每个人到达时，已经开花的花的数目，减去在每个人到达时，已经凋谢的花的数目，即可得到答案。
+
+时间复杂度 $O((m + n) \times \log n)$，空间复杂度 $O(n)$。其中 $n$ 和 $m$ 分别是数组 $flowers$ 和 $persons$ 的长度。
+
+**方法二：差分 + 排序 + 离线查询**
+
+我们可以利用差分来维护每个时间点的花的数目。接下来，我们将 $persons$ 按照到达时间从小到大排序，在每个人到达时，我们对差分数组进行前缀和运算，就可以得到答案。
+
+时间复杂度 $O(m \times \log m + n \times \log n)$，空间复杂度 $O(n + m)$。其中 $n$ 和 $m$ 分别是数组 $flowers$ 和 $persons$ 的长度。
 
 <!-- tabs:start -->
 
@@ -72,38 +75,262 @@ class Solution:
         return [bisect_right(start, p) - bisect_left(end, p) for p in persons]
 ```
 
+```python
+class Solution:
+    def fullBloomFlowers(self, flowers: List[List[int]], people: List[int]) -> List[int]:
+        d = defaultdict(int)
+        for st, ed in flowers:
+            d[st] += 1
+            d[ed + 1] -= 1
+        ts = sorted(d)
+        s = i = 0
+        m = len(people)
+        ans = [0] * m
+        for t, j in sorted(zip(people, range(m))):
+            while i < len(ts) and ts[i] <= t:
+                s += d[ts[i]]
+                i += 1
+            ans[j] = s
+        return ans
+```
+
 ### **Java**
 
 <!-- 这里可写当前语言的特殊实现逻辑 -->
 
 ```java
+class Solution {
+    public int[] fullBloomFlowers(int[][] flowers, int[] people) {
+        int n = flowers.length;
+        int[] start = new int[n];
+        int[] end = new int[n];
+        for (int i = 0; i < n; ++i) {
+            start[i] = flowers[i][0];
+            end[i] = flowers[i][1];
+        }
+        Arrays.sort(start);
+        Arrays.sort(end);
+        int m = people.length;
+        int[] ans = new int[m];
+        for (int i = 0; i < m; ++i) {
+            ans[i] = search(start, people[i] + 1) - search(end, people[i]);
+        }
+        return ans;
+    }
+
+    private int search(int[] nums, int x) {
+        int l = 0, r = nums.length;
+        while (l < r) {
+            int mid = (l + r) >> 1;
+            if (nums[mid] >= x) {
+                r = mid;
+            } else {
+                l = mid + 1;
+            }
+        }
+        return l;
+    }
+}
+```
+
+```java
+class Solution {
+    public int[] fullBloomFlowers(int[][] flowers, int[] people) {
+        TreeMap<Integer, Integer> d = new TreeMap<>();
+        for (int[] f : flowers) {
+            d.merge(f[0], 1, Integer::sum);
+            d.merge(f[1] + 1, -1, Integer::sum);
+        }
+        int s = 0;
+        int m = people.length;
+        Integer[] idx = new Integer[m];
+        for (int i = 0; i < m; i++) {
+            idx[i] = i;
+        }
+        Arrays.sort(idx, Comparator.comparingInt(i -> people[i]));
+        int[] ans = new int[m];
+        for (int i : idx) {
+            int t = people[i];
+            while (!d.isEmpty() && d.firstKey() <= t) {
+                s += d.pollFirstEntry().getValue();
+            }
+            ans[i] = s;
+        }
+        return ans;
+    }
+}
+```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    vector<int> fullBloomFlowers(vector<vector<int>>& flowers, vector<int>& people) {
+        int n = flowers.size();
+        vector<int> start;
+        vector<int> end;
+        for (auto& f : flowers) {
+            start.push_back(f[0]);
+            end.push_back(f[1]);
+        }
+        sort(start.begin(), start.end());
+        sort(end.begin(), end.end());
+        vector<int> ans;
+        for (auto& p : people) {
+            auto r = upper_bound(start.begin(), start.end(), p) - start.begin();
+            auto l = lower_bound(end.begin(), end.end(), p) - end.begin();
+            ans.push_back(r - l);
+        }
+        return ans;
+    }
+};
+```
+
+```cpp
+class Solution {
+public:
+    vector<int> fullBloomFlowers(vector<vector<int>>& flowers, vector<int>& people) {
+        map<int, int> d;
+        for (auto& f : flowers) {
+            d[f[0]]++;
+            d[f[1] + 1]--;
+        }
+        int m = people.size();
+        vector<int> idx(m);
+        iota(idx.begin(), idx.end(), 0);
+        sort(idx.begin(), idx.end(), [&](int i, int j) {
+            return people[i] < people[j];
+        });
+        vector<int> ans(m);
+        int s = 0;
+        for (int i : idx) {
+            int t = people[i];
+            while (!d.empty() && d.begin()->first <= t) {
+                s += d.begin()->second;
+                d.erase(d.begin());
+            }
+            ans[i] = s;
+        }
+        return ans;
+    }
+};
+```
+
+### **Go**
+
+```go
+func fullBloomFlowers(flowers [][]int, people []int) (ans []int) {
+	n := len(flowers)
+	start := make([]int, n)
+	end := make([]int, n)
+	for i, f := range flowers {
+		start[i] = f[0]
+		end[i] = f[1]
+	}
+	sort.Ints(start)
+	sort.Ints(end)
+	for _, p := range people {
+		r := sort.SearchInts(start, p+1)
+		l := sort.SearchInts(end, p)
+		ans = append(ans, r-l)
+	}
+	return
+}
+```
+
+```go
+func fullBloomFlowers(flowers [][]int, people []int) []int {
+	d := map[int]int{}
+	for _, f := range flowers {
+		d[f[0]]++
+		d[f[1]+1]--
+	}
+	ts := []int{}
+	for t := range d {
+		ts = append(ts, t)
+	}
+	sort.Ints(ts)
+	m := len(people)
+	idx := make([]int, m)
+	for i := range idx {
+		idx[i] = i
+	}
+	sort.Slice(idx, func(i, j int) bool { return people[idx[i]] < people[idx[j]] })
+	ans := make([]int, m)
+	s, i := 0, 0
+	for _, j := range idx {
+		t := people[j]
+		for i < len(ts) && ts[i] <= t {
+			s += d[ts[i]]
+			i++
+		}
+		ans[j] = s
+	}
+	return ans
+}
 ```
 
 ### **TypeScript**
 
 ```ts
-function fullBloomFlowers(flowers: number[][], persons: number[]): number[] {
-    // 离散差分
-    let hashMap = new Map();
-    for (let [start, end] of flowers) {
-        end++;
-        hashMap.set(start, (hashMap.get(start) || 0) + 1);
-        hashMap.set(end, (hashMap.get(end) || 0) - 1);
+function fullBloomFlowers(flowers: number[][], people: number[]): number[] {
+    const n = flowers.length;
+    const start = new Array(n).fill(0);
+    const end = new Array(n).fill(0);
+    for (let i = 0; i < n; ++i) {
+        start[i] = flowers[i][0];
+        end[i] = flowers[i][1];
+    }
+    start.sort((a, b) => a - b);
+    end.sort((a, b) => a - b);
+    const ans: number[] = [];
+    for (const p of people) {
+        const r = search(start, p + 1);
+        const l = search(end, p);
+        ans.push(r - l);
     }
-    for (let p of persons) {
-        if (!hashMap.has(p)) {
-            hashMap.set(p, 0);
+    return ans;
+}
+
+function search(nums: number[], x: number): number {
+    let l = 0;
+    let r = nums.length;
+    while (l < r) {
+        const mid = (l + r) >> 1;
+        if (nums[mid] >= x) {
+            r = mid;
+        } else {
+            l = mid + 1;
         }
     }
-    let keys = Array.from(hashMap.keys()).sort((a, b) => a - b);
-    let pre = 0;
-    for (let k of keys) {
-        pre += hashMap.get(k);
-        hashMap.set(k, pre);
+    return l;
+}
+```
+
+```ts
+function fullBloomFlowers(flowers: number[][], people: number[]): number[] {
+    const d: Map<number, number> = new Map();
+    for (const [st, ed] of flowers) {
+        d.set(st, (d.get(st) || 0) + 1);
+        d.set(ed + 1, (d.get(ed + 1) || 0) - 1);
+    }
+    const ts = [...d.keys()].sort((a, b) => a - b);
+    let s = 0;
+    let i = 0;
+    const m = people.length;
+    const idx: number[] = [...Array(m)]
+        .map((_, i) => i)
+        .sort((a, b) => people[a] - people[b]);
+    const ans = Array(m).fill(0);
+    for (const j of idx) {
+        const t = people[j];
+        while (i < ts.length && ts[i] <= t) {
+            s += d.get(ts[i])!;
+            ++i;
+        }
+        ans[j] = s;
     }
-    // 离散查询
-    let ans = persons.map(v => hashMap.get(v));
     return ans;
 }
 ```