From 17541976f66849925280c2d162b12c947eb9c314 Mon Sep 17 00:00:00 2001
From: ale8k <alexanderkilroy@outlook.com>
Date: Wed, 8 Dec 2021 21:32:25 +0000
Subject: [PATCH] Interpolation search

---
 .../interpolation_search.go                   | 37 +++++++++++++++
 .../interpolation_search_test.go              | 47 +++++++++++++++++++
 2 files changed, 84 insertions(+)
 create mode 100644 slice_searching/interpolation_search/interpolation_search.go
 create mode 100644 slice_searching/interpolation_search/interpolation_search_test.go

diff --git a/slice_searching/interpolation_search/interpolation_search.go b/slice_searching/interpolation_search/interpolation_search.go
new file mode 100644
index 0000000..2c24779
--- /dev/null
+++ b/slice_searching/interpolation_search/interpolation_search.go
@@ -0,0 +1,37 @@
+package interpolationsearch
+
+// Runs a search based on interpolation
+func InterpolationSearch(param int, slice []int) int {
+	if param < 0 {
+		return -1
+	}
+	low := 0
+	mid := -1
+	high := len(slice) - 1
+
+	for {
+
+		if low == high || slice[low] == slice[high] {
+			return -1
+		}
+
+		//	 		((Hi -  Lo)/(slice[Hi]  -slice[Lo]     ))*(X-slice[Lo])
+		mid = low + ((high-low)/(slice[high]-slice[low]))*(param-slice[low])
+
+		// where −
+		// 	A    = list
+		// 	Lo   = Lowest index of the list
+		// 	Hi   = Highest index of the list
+		// 	A[n] = Value stored at index n in the list
+
+		if slice[mid] == param {
+			return mid
+		} else {
+			if slice[mid] < param {
+				low = mid + 1
+			} else if slice[mid] > param {
+				high = mid - 1
+			}
+		}
+	}
+}
diff --git a/slice_searching/interpolation_search/interpolation_search_test.go b/slice_searching/interpolation_search/interpolation_search_test.go
new file mode 100644
index 0000000..e76154c
--- /dev/null
+++ b/slice_searching/interpolation_search/interpolation_search_test.go
@@ -0,0 +1,47 @@
+package interpolationsearch
+
+import "testing"
+
+func TestInterpolationSearch(t *testing.T) {
+	type args struct {
+		param int
+		slice []int
+	}
+	tests := []struct {
+		name string
+		args args
+		want int
+	}{
+		{
+			name: "it correctly finds the expected index",
+			args: args{
+				param: 4,
+				slice: []int{2, 4, 6},
+			},
+			want: 1,
+		},
+		{
+			name: "it returns -1 when out of bounds > length",
+			args: args{
+				param: 10,
+				slice: []int{6, 8, 2, 4, 6},
+			},
+			want: -1,
+		},
+		{
+			name: "it returns -1 when mid < 0",
+			args: args{
+				param: -1,
+				slice: []int{6, 8, 2, 4, 6},
+			},
+			want: -1,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := InterpolationSearch(tt.args.param, tt.args.slice); got != tt.want {
+				t.Errorf("InterpolationSearch() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}