From e8b3d679818f69cd4bac75ae4bb578bd6343fc65 Mon Sep 17 00:00:00 2001
From: VicRen <vic.ren@me.com>
Date: Sat, 17 Oct 2020 21:48:29 +0800
Subject: [PATCH] 18: maximum path sum I

---
 18_maximum_path_sum_I/digits.txt              | 15 +++++
 18_maximum_path_sum_I/main.go                 | 64 +++++++++++++++++++
 .../maximum_path_sum_test.go                  | 43 +++++++++++++
 3 files changed, 122 insertions(+)
 create mode 100644 18_maximum_path_sum_I/digits.txt
 create mode 100644 18_maximum_path_sum_I/main.go
 create mode 100644 18_maximum_path_sum_I/maximum_path_sum_test.go

diff --git a/18_maximum_path_sum_I/digits.txt b/18_maximum_path_sum_I/digits.txt
new file mode 100644
index 0000000..bc0ed83
--- /dev/null
+++ b/18_maximum_path_sum_I/digits.txt
@@ -0,0 +1,15 @@
+75
+95 64
+17 47 82
+18 35 87 10
+20 04 82 47 65
+19 01 23 75 03 34
+88 02 77 73 07 63 67
+99 65 04 28 06 16 70 92
+41 41 26 56 83 40 80 70 33
+41 48 72 33 47 32 37 16 94 29
+53 71 44 65 25 43 91 52 97 51 14
+70 11 33 28 77 73 17 78 39 68 17 57
+91 71 52 38 17 14 91 43 58 50 27 29 48
+63 66 04 68 89 53 67 30 73 16 69 87 40 31
+04 62 98 27 23 09 70 98 73 93 38 53 60 04 23
\ No newline at end of file
diff --git a/18_maximum_path_sum_I/main.go b/18_maximum_path_sum_I/main.go
new file mode 100644
index 0000000..de233d0
--- /dev/null
+++ b/18_maximum_path_sum_I/main.go
@@ -0,0 +1,64 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strconv"
+	"strings"
+)
+
+func main() {
+	fi, err := os.Open("./digits.txt")
+	if err != nil {
+		panic(err)
+	}
+	defer fi.Close()
+
+	br := bufio.NewReader(fi)
+	var input [][]int
+	for {
+		a, _, e := br.ReadLine()
+		if e == io.EOF {
+			break
+		}
+		got := strings.Split(string(a), " ")
+		var line []int
+		for _, v := range got {
+			n, err := strconv.Atoi(v)
+			if err != nil {
+				panic(err)
+			}
+			line = append(line, n)
+		}
+		input = append(input, line)
+	}
+	fmt.Println("input=", input)
+
+	fmt.Println("maximum path sum is:", LargestSumOfTriangle(input))
+}
+
+func LargestSumOfTriangle(input [][]int) int {
+	rest := input
+	l := len(input)
+	for l > 1 {
+		hl := l - 2
+		var line []int
+		for n, v := range input[l-2] {
+			x := v + max(input[l-1][n], input[l-1][n+1])
+			line = append(line, x)
+		}
+		rest = rest[:hl]
+		rest = append(rest, line)
+		l = len(rest)
+	}
+	return rest[0][0]
+}
+
+func max(x, y int) int {
+	if x > y {
+		return x
+	}
+	return y
+}
diff --git a/18_maximum_path_sum_I/maximum_path_sum_test.go b/18_maximum_path_sum_I/maximum_path_sum_test.go
new file mode 100644
index 0000000..53095b1
--- /dev/null
+++ b/18_maximum_path_sum_I/maximum_path_sum_test.go
@@ -0,0 +1,43 @@
+package main
+
+import (
+	"testing"
+)
+
+func TestLargestSumOfTriangle(t *testing.T) {
+	tt := []struct {
+		name  string
+		input [][]int
+		want  int
+	}{
+		{
+			"example",
+			[][]int{{3}, {7, 4}, {2, 4, 6}, {8, 5, 9, 3}},
+			23,
+		},
+		{
+			"example_2",
+			[][]int{{3}, {7, 4}},
+			10,
+		},
+		{
+			"example_3",
+			[][]int{{3}},
+			3,
+		},
+		{
+			"example_4",
+			[][]int{{3}, {7, 4}, {2, 4, 6}},
+			14,
+		},
+	}
+
+	for _, tc := range tt {
+		t.Run(tc.name, func(t *testing.T) {
+			got := LargestSumOfTriangle(tc.input)
+			if got != tc.want {
+				t.Errorf("LargestSumOfTriangle(%v)=%d, want %d", tc.input, got, tc.want)
+			}
+		})
+	}
+}