Merge pull request #34 from ridwanfathin/graph_fw

add flowd-warshall algorithm

graph/shortest_distance_fw.go

@@ -0,0 +1,57 @@
+// shortest distances between every pair of vertices using floyd-warshall algorithm
+// https://en.wikipedia.org/wiki/Floyd%E2%80%93Warshall_algorithm
+// http://www.golangprograms.com/golang-program-for-implementation-of-floyd-warshall-algorithm.html
+package graph
+
+import (
+	"fmt"
+	"math"
+)
+
+type graph struct {
+	to int
+	wt float64
+}
+
+func floydWarshall(g [][]graph) [][]float64 {
+	dist := make([][]float64, len(g))
+	for i := range dist {
+		di := make([]float64, len(g))
+		for j := range di {
+			di[j] = math.Inf(1)
+		}
+		di[i] = 0
+		dist[i] = di
+	}
+	for u, graphs := range g {
+		for _, v := range graphs {
+			dist[u][v.to] = v.wt
+		}
+	}
+	for k, dk := range dist {
+		for _, di := range dist {
+			for j, dij := range di {
+				if d := di[k] + dk[j]; dij > d {
+					di[j] = d
+				}
+			}
+		}
+	}
+	return dist
+}
+
+func main() {
+	gra := [][]graph{
+		1: {{2, 3}, {3, 8}, {5, -4}},
+		2: {{4, 1}, {5, 7}},
+		3: {{2, 4}},
+		4: {{1, 2}, {3, -5}},
+		5: {{4, 6}},
+	}
+
+	dist := floydWarshall(gra)
+	//dist[][] will be the output matrix that will have the shortest distances between every pair of vertices
+	for _, d := range dist {
+		fmt.Printf("%4g\n", d)
+	}
+}

numerical/max_sub_array.go

@@ -0,0 +1,31 @@
+package numerical
+
+import (
+	"fmt"
+)
+
+/* O(n) solution for calculating maximum subarray sum. */
+func Max(x int, y int) int {
+	if x < y {
+		return y
+	}
+	return x
+}
+
+func maxSubarray(array []int) int {
+	var currentMax int = 0
+	var maxTillNow int = 0
+	for _, v := range array {
+		currentMax = Max(v, currentMax+v)
+		maxTillNow = Max(maxTillNow, currentMax)
+	}
+	return maxTillNow
+}
+
+func main() {
+	array := []int{-3, -4, 7, 1, -2, 0, -5, 1, 0, 6, -5}
+	fmt.Println("Maximum subarray sum: ", maxSubarray(array))
+
+	array = []int{3, 4, -7, 2, 0, 0, -3, -1, 0, -5, 7}
+	fmt.Println("Maximum subarray sum: ", maxSubarray(array))
+}

numerical/swap.go

@@ -0,0 +1,15 @@
+package numerical
+
+import "fmt"
+
+func swap(x, y *int) {
+	*x, *y = *y, *x
+}
+
+func main() {
+	x := 3
+	y := 2
+	fmt.Println(x, y)
+	swap(&x, &y)
+	fmt.Println(x, y)
+}

numerical/swap_test.go

@@ -0,0 +1,19 @@
+package numerical
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSwap(t *testing.T) {
+	x := 5
+	y := 6
+
+	expectedX := 6
+	expectedY := 5
+
+	swap(&x, &y)
+	assert.Equal(t, x, expectedX, "value should be equal")
+	assert.Equal(t, y, expectedY, "value should be equal")
+}