Merge 439ba1c into 09090b0

README.md

@@ -94,3 +94,4 @@ problems from
 * [Day 82](https://github.com/vaskoz/dailycodingproblem-go/issues/173)
 * [Day 83](https://github.com/vaskoz/dailycodingproblem-go/issues/175)
 * [Day 84](https://github.com/vaskoz/dailycodingproblem-go/issues/177)
+* [Day 85](https://github.com/vaskoz/dailycodingproblem-go/issues/179)

day85/problem.go

@@ -0,0 +1,14 @@
+package day85
+
+// MathematicalIf returns x if b=1 and y if b=0.
+func MathematicalIf(x, y, b int32) int32 {
+	var xMask, yMask int32
+	xMask = b
+	xMask |= xMask << 1
+	xMask |= xMask << 2
+	xMask |= xMask << 4
+	xMask |= xMask << 8
+	xMask |= xMask << 16
+	yMask = ^xMask
+	return (x & xMask) | (y & yMask)
+}

day85/problem_test.go

@@ -0,0 +1,31 @@
+package day85
+
+import "testing"
+
+var testcases = []struct {
+	x, y, b, expected int32
+}{
+	{10, 20, 1, 10},
+	{10, 20, 0, 20},
+	{-20, -40, 1, -20},
+	{-20, -40, 0, -40},
+	{100, -200, 1, 100},
+	{100, -200, 0, -200},
+}
+
+func TestMathematicalIf(t *testing.T) {
+	t.Parallel()
+	for _, tc := range testcases {
+		if result := MathematicalIf(tc.x, tc.y, tc.b); tc.expected != result {
+			t.Errorf("x(%d),y(%d),b(%d),expected(%d),got(%d)", tc.x, tc.y, tc.b, tc.expected, result)
+		}
+	}
+}
+
+func BenchmarkMathematicalIf(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		for _, tc := range testcases {
+			MathematicalIf(tc.x, tc.y, tc.b)
+		}
+	}
+}