max-product.go

package maxproduct

import "fmt"

// find max product of 3 numbers
func maxProduct(ints []int) int {
	// scan for 3 max values and 2 smallest numbers (possible negative)
	max := 0
	// 32 bit
	minVal := 1<<31 - 1
	maxVal := 1<<31 - 1
	var max1, max2, max3 = -maxVal, -maxVal, -maxVal
	var min1, min2 = minVal, minVal

	for _, v := range ints {
		if v >= max1 {
			max1, max2, max3 = v, max1, max2
		} else if v >= max2 {
			max2, max3 = v, max2
		} else if v >= max3 {
			max3 = v
		}

		if v <= min1 {
			min1, min2 = v, min1
		} else if v <= min2 {
			min2 = v
		}
	}
	fmt.Printf("%d %d %d\n", max1, max2, max3) // output for debug
	fmt.Printf("%d %d \n", min1, min2)         // output for debug
	if max1*max2*max3 > min1*min2*max1 {
		max = max1 * max2 * max3
	} else {
		max = min1 * min2 * max1
	}

	return max
}
/*
package maxproduct

import (
	"testing"
)

func TestMaxProduct(t *testing.T) {
	cases := []struct {
		in   []int
		want int
	}{
		{in: []int{-5, 3, 2, 10}, want: 60},
		{in: []int{-5, -3, -4, 2, 2, 10}, want: 200},
	}

	for i, tc := range cases {
		out := maxProduct(tc.in)
		if tc.want != out {
			t.Errorf("case %d, want %d, got %d", i, tc.want, out)
		}

	}

}
*/