Merge pull request #646 from openset/develop

Add: 4Sum II

Author: Shuo

problems/4sum-ii/4sum_ii.go

@@ -1 +1,17 @@
 package p_4sum_ii
+
+func fourSumCount(A []int, B []int, C []int, D []int) int {
+	ans, n := 0, len(A)
+	sum := make(map[int]int, n*n)
+	for i := 0; i < n; i++ {
+		for j := 0; j < n; j++ {
+			sum[A[i]+B[j]]++
+		}
+	}
+	for k := 0; k < n; k++ {
+		for l := 0; l < n; l++ {
+			ans += sum[-C[k]-D[l]]
+		}
+	}
+	return ans
+}

problems/4sum-ii/4sum_ii_test.go

@@ -1 +1,29 @@
 package p_4sum_ii
+
+import "testing"
+
+type caseType struct {
+	a        []int
+	b        []int
+	c        []int
+	d        []int
+	expected int
+}
+
+func TestFourSumCount(t *testing.T) {
+	tests := [...]caseType{
+		{
+			a:        []int{1, 2},
+			b:        []int{-2, -1},
+			c:        []int{-1, 2},
+			d:        []int{0, 2},
+			expected: 2,
+		},
+	}
+	for _, tc := range tests {
+		output := fourSumCount(tc.a, tc.b, tc.c, tc.d)
+		if output != tc.expected {
+			t.Fatalf("input: %v, output: %v, expected: %v", tc, output, tc.expected)
+		}
+	}
+}