2026-03-07 00:47

Author: SilverRainZ

src/notes/writeups/leetcode/index.rst

@@ -868,3 +868,15 @@ Ones and Zeroes
 
 .. [#] https://twitter.com/mxcl/status/608682016205344768
 .. [#] https://oi-wiki.org/ds/monotonous-stack/
+
+Merge Sorted Array
+------------------
+
+.. leetcode:: _
+   :id: merge-sorted-array
+   :diffculty: Easy
+   :language: go
+   :key: 排序
+   :date: 2026-03-05
+
+很简单的一道题，要不先把 nums1 挪开然后直接合并，要不逆序。之前想复杂了。

src/notes/writeups/leetcode/merge-sorted-array/go.mod

@@ -0,0 +1,3 @@
+module merge-sorted-array
+
+go 1.25.0

src/notes/writeups/leetcode/merge-sorted-array/main.go

@@ -0,0 +1,25 @@
+package main
+
+func merge(nums1 []int, m int, nums2 []int, n int)  {
+	p1, p2 := m-1, n-1
+	p := m+n-1
+	res := nums1
+
+	for p1 >= 0 && p2 >= 0 {
+		if nums1[p1] > nums2[p2] {
+			res[p] = nums1[p1] 
+			p1--
+		} else {
+			res[p] = nums2[p2] 
+			p2--
+		}
+		p--
+	}
+
+	if p1 < 0 && p2 >= 0 {
+		copy(res[0:p+1], nums2[:p2+1])
+	}
+	if p2 < 0 && p1 <= 0 {
+		copy(res[0:p+1], nums1[:p1+1])
+	}
+}

src/notes/writeups/leetcode/merge-sorted-array/main_test.go

@@ -0,0 +1,101 @@
+package main
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestMerge(t *testing.T) {
+	tests := []struct {
+		name     string
+		nums1    []int
+		m        int
+		nums2    []int
+		n        int
+		expected []int
+	}{
+		{
+			name:     "basic merge",
+			nums1:    []int{1, 2, 3, 0, 0, 0},
+			m:        3,
+			nums2:    []int{4, 5, 6},
+			n:        3,
+			expected: []int{1, 2, 3, 4, 5, 6},
+		},
+		{
+			name:     "basic merge1",
+			nums1:    []int{4, 5, 6, 0, 0, 0},
+			m:        3,
+			nums2:    []int{1, 2, 3},
+			n:        3,
+			expected: []int{1, 2, 3, 4, 5, 6},
+		},
+		{
+			name:     "basic merge2",
+			nums1:    []int{1, 2, 3, 0, 0, 0},
+			m:        3,
+			nums2:    []int{2, 5, 6},
+			n:        3,
+			expected: []int{1, 2, 2, 3, 5, 6},
+		},
+		{
+			name:     "basic merge3",
+			nums1:    []int{4, 5, 6, 0, 0, 0},
+			m:        3,
+			nums2:    []int{1, 2, 10},
+			n:        3,
+			expected: []int{1, 2, 4, 5, 6, 10},
+		},
+		{
+			name:     "nums1 is empty",
+			nums1:    []int{0, 0, 0},
+			m:        0,
+			nums2:    []int{1, 2, 3},
+			n:        3,
+			expected: []int{1, 2, 3},
+		},
+		{
+			name:     "nums2 is empty",
+			nums1:    []int{1, 2, 3},
+			m:        3,
+			nums2:    []int{},
+			n:        0,
+			expected: []int{1, 2, 3},
+		},
+		{
+			name:     "all nums2 elements smaller",
+			nums1:    []int{4, 5, 6, 0, 0, 0},
+			m:        3,
+			nums2:    []int{1, 2, 3},
+			n:        3,
+			expected: []int{1, 2, 3, 4, 5, 6},
+		},
+		{
+			name:     "all nums1 elements smaller",
+			nums1:    []int{1, 2, 3, 0, 0, 0},
+			m:        3,
+			nums2:    []int{4, 5, 6},
+			n:        3,
+			expected: []int{1, 2, 3, 4, 5, 6},
+		},
+		{
+			name:     "single element merge",
+			nums1:    []int{1, 0},
+			m:        1,
+			nums2:    []int{0},
+			n:        1,
+			expected: []int{0, 1},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			nums1Copy := make([]int, len(tt.nums1))
+			copy(nums1Copy, tt.nums1)
+			merge(nums1Copy, tt.m, tt.nums2, tt.n)
+			if !reflect.DeepEqual(nums1Copy, tt.expected) {
+				t.Errorf("merge() = %v, want %v", nums1Copy, tt.expected)
+			}
+		})
+	}
+}