leetcode: 881. Boats to Save People | Greedy | Two Pointers

leetcode/0881-boats-to-save-people/README.md

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+# 881. Boats to Save People
+
+You are given an array people where `people[i]` is the weight of the `ith` person, and an **infinite number of boats** where each boat can carry a maximum weight of `limit`. Each boat carries at most two people at the same time, provided the sum of the weight of those people is at most `limit`.
+
+*Return the minimum number of boats to carry every given person.*
+
+**Example:**
+```
+Input: people = [1,2], limit = 3
+Output: 1
+Explanation: 1 boat (1, 2)
+```
+
+**Constraints:**
+- `1 <= people.length <= 5 * 10^4`
+- `1 <= people[i] <= limit <= 3 * 10^4`

leetcode/0881-boats-to-save-people/num_rescue_boats.go

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+package leetcode
+
+import "sort"
+
+func numRescueBoats(people []int, limit int) int {
+	sort.Ints(people)
+	i, j := 0, len(people)-1
+	boats := 0
+	for i <= j {
+		if people[i]+people[j] <= limit {
+			i++
+		}
+		j--
+		boats++
+	}
+	return boats
+}

leetcode/0881-boats-to-save-people/num_rescue_boats_test.go

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+package leetcode
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestNumRescueBoats(t *testing.T) {
+	assert := assert.New(t)
+	for _, test := range tests {
+		assert.Equal(test.expected, numRescueBoats(test.people, test.limit))
+	}
+}
+
+var tests = []struct {
+	people   []int
+	limit    int
+	expected int
+}{
+	{
+		people:   []int{1, 2},
+		limit:    3,
+		expected: 1,
+	},
+	{
+		people:   []int{3, 2, 2, 1},
+		limit:    3,
+		expected: 3,
+	},
+	{
+		people:   []int{3, 5, 3, 4},
+		limit:    5,
+		expected: 4,
+	},
+}