Sri Hari: Batch-4/Neetcode-All/Added-articles

articles/boats-to-save-people.md

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+## 1. Sorting + Two Pointers
+
+::tabs-start
+
+```python
+class Solution:
+    def numRescueBoats(self, people: List[int], limit: int) -> int:
+        people.sort()
+        res, l, r = 0, 0, len(people) - 1
+        while l <= r:
+            remain = limit - people[r]
+            r -= 1
+            res += 1
+            if l <= r and remain >= people[l]:
+                l += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int numRescueBoats(int[] people, int limit) {
+        Arrays.sort(people);
+        int res = 0, l = 0, r = people.length - 1;
+        while (l <= r) {
+            int remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numRescueBoats(vector<int>& people, int limit) {
+        sort(people.begin(), people.end());
+        int res = 0, l = 0, r = people.size() - 1;
+        while (l <= r) {
+            int remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} people
+     * @param {number} limit
+     * @return {number}
+     */
+    numRescueBoats(people, limit) {
+        people.sort((a, b) => a - b);
+        let res = 0, l = 0, r = people.length - 1;
+        while (l <= r) {
+            let remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n \log n)$
+* Space complexity: $O(1)$ or $O(n)$ depending on the sorting algorithm.
+
+---
+
+## 2. Counting Sort
+
+::tabs-start
+
+```python
+class Solution:
+    def numRescueBoats(self, people: List[int], limit: int) -> int:
+        m = max(people)
+        count = [0] * (m + 1)
+        for p in people:
+            count[p] += 1
+
+        idx, i = 0, 1
+        while idx < len(people):
+            while count[i] == 0:
+                i += 1
+            people[idx] = i
+            count[i] -= 1
+            idx += 1
+
+        res, l, r = 0, 0, len(people) - 1
+        while l <= r:
+            remain = limit - people[r]
+            r -= 1
+            res += 1
+            if l <= r and remain >= people[l]:
+                l += 1
+        return res
+```
+
+```java
+public class Solution {
+    public int numRescueBoats(int[] people, int limit) {
+        int m = Arrays.stream(people).max().getAsInt();
+        int[] count = new int[m + 1];
+        for (int p : people) {
+            count[p]++;
+        }
+
+        int idx = 0, i = 1;
+        while (idx < people.length) {
+            while (count[i] == 0) {
+                i++;
+            }
+            people[idx++] = i;
+            count[i]--;
+        }
+
+        int res = 0, l = 0, r = people.length - 1;
+        while (l <= r) {
+            int remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+```cpp
+class Solution {
+public:
+    int numRescueBoats(vector<int>& people, int limit) {
+        int m = *max_element(people.begin(), people.end());
+        vector<int> count(m + 1, 0);
+        for (int p : people) {
+            count[p]++;
+        }
+
+        int idx = 0, i = 1;
+        while (idx < people.size()) {
+            while (count[i] == 0) {
+                i++;
+            }
+            people[idx++] = i;
+            count[i]--;
+        }
+
+        int res = 0, l = 0, r = people.size() - 1;
+        while (l <= r) {
+            int remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+};
+```
+
+```javascript
+class Solution {
+    /**
+     * @param {number[]} people
+     * @param {number} limit
+     * @return {number}
+     */
+    numRescueBoats(people, limit) {
+        const m = Math.max(...people);
+        const count = new Array(m + 1).fill(0);
+        for (const p of people) {
+            count[p]++;
+        }
+
+        let idx = 0, i = 1;
+        while (idx < people.length) {
+            while (count[i] === 0) {
+                i++;
+            }
+            people[idx++] = i;
+            count[i]--;
+        }
+
+        let res = 0, l = 0, r = people.length - 1;
+        while (l <= r) {
+            const remain = limit - people[r--];
+            res++;
+            if (l <= r && remain >= people[l]) {
+                l++;
+            }
+        }
+        return res;
+    }
+}
+```
+
+::tabs-end
+
+### Time & Space Complexity
+
+* Time complexity: $O(n)$
+* Space complexity: $O(m)$
+
+> Where $n$ is the size of the input array and $m$ is the maximum value in the array.