Add: Arranging Coins

Author: openset

problems/arranging-coins/arranging_coins.go

@@ -1 +1,8 @@
-package arranging_coins
+package problem_441
+
+import "math"
+
+func arrangeCoins(n int) int {
+	x := math.Sqrt(1+8*float64(n)) - 1
+	return int(x) / 2
+}

problems/arranging-coins/arranging_coins_test.go

@@ -1 +1,51 @@
-package arranging_coins
+package problem_441
+
+import "testing"
+
+type caseType struct {
+	input    int
+	expected int
+}
+
+func TestArrangeCoins(t *testing.T) {
+	tests := [...]caseType{
+		{
+			input:    5,
+			expected: 2,
+		},
+		{
+			input:    8,
+			expected: 3,
+		},
+		{
+			input:    0,
+			expected: 0,
+		},
+		{
+			input:    1,
+			expected: 1,
+		},
+		{
+			input:    2,
+			expected: 1,
+		},
+		{
+			input:    3,
+			expected: 2,
+		},
+		{
+			input:    13,
+			expected: 4,
+		},
+		{
+			input:    130,
+			expected: 15,
+		},
+	}
+	for _, tc := range tests {
+		output := arrangeCoins(tc.input)
+		if output != tc.expected {
+			t.Fatalf("input: %v, output: %v, expected: %v", tc.input, output, tc.expected)
+		}
+	}
+}