From 4f3e7e5b98395599f2943d5ef221c4098c7d660a Mon Sep 17 00:00:00 2001
From: YDZ <ydz627@gmail.com>
Date: Thu, 1 Aug 2019 20:08:09 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20problem=20778?=
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---
 .../778. Swim in Rising Water.go              | 62 +++++++++++++++++++
 .../778. Swim in Rising Water_test.go         | 46 ++++++++++++++
 2 files changed, 108 insertions(+)
 create mode 100644 Algorithms/0778. Swim in Rising Water/778. Swim in Rising Water.go
 create mode 100644 Algorithms/0778. Swim in Rising Water/778. Swim in Rising Water_test.go

diff --git a/Algorithms/0778. Swim in Rising Water/778. Swim in Rising Water.go b/Algorithms/0778. Swim in Rising Water/778. Swim in Rising Water.go
new file mode 100644
index 00000000..3277b3e3
--- /dev/null
+++ b/Algorithms/0778. Swim in Rising Water/778. Swim in Rising Water.go	
@@ -0,0 +1,62 @@
+package leetcode
+
+// 解法一 DFS + 二分
+func swimInWater(grid [][]int) int {
+	row, col, flags, minWait, maxWait := len(grid), len(grid[0]), make([][]int, len(grid)), 0, 0
+	for i, row := range grid {
+		flags[i] = make([]int, len(row))
+		for j := 0; j < col; j++ {
+			flags[i][j] = -1
+			if row[j] > maxWait {
+				maxWait = row[j]
+			}
+		}
+	}
+	for minWait < maxWait {
+		midWait := (minWait + maxWait) / 2
+		addFlags(grid, flags, midWait, 0, 0)
+		if flags[row-1][col-1] == midWait {
+			maxWait = midWait
+		} else {
+			minWait = midWait + 1
+		}
+	}
+	return minWait
+}
+
+func addFlags(grid [][]int, flags [][]int, flag int, row int, col int) {
+	if row < 0 || col < 0 || row >= len(grid) || col >= len(grid[0]) {
+		return
+	}
+	if grid[row][col] > flag || flags[row][col] == flag {
+		return
+	}
+	flags[row][col] = flag
+	addFlags(grid, flags, flag, row-1, col)
+	addFlags(grid, flags, flag, row+1, col)
+	addFlags(grid, flags, flag, row, col-1)
+	addFlags(grid, flags, flag, row, col+1)
+}
+
+// 解法二 并查集(并不是此题的最优解)
+func swimInWater1(grid [][]int) int {
+	n, uf, res := len(grid), UnionFind{}, 0
+	uf.init(n * n)
+	for uf.find(0) != uf.find(n*n-1) {
+		for i := 0; i < n; i++ {
+			for j := 0; j < n; j++ {
+				if grid[i][j] > res {
+					continue
+				}
+				if i < n-1 && grid[i+1][j] <= res {
+					uf.union(i*n+j, i*n+j+n)
+				}
+				if j < n-1 && grid[i][j+1] <= res {
+					uf.union(i*n+j, i*n+j+1)
+				}
+			}
+		}
+		res++
+	}
+	return res - 1
+}
diff --git a/Algorithms/0778. Swim in Rising Water/778. Swim in Rising Water_test.go b/Algorithms/0778. Swim in Rising Water/778. Swim in Rising Water_test.go
new file mode 100644
index 00000000..d78aeff2
--- /dev/null
+++ b/Algorithms/0778. Swim in Rising Water/778. Swim in Rising Water_test.go	
@@ -0,0 +1,46 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question778 struct {
+	para778
+	ans778
+}
+
+// para 是参数
+// one 代表第一个参数
+type para778 struct {
+	grid [][]int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans778 struct {
+	one int
+}
+
+func Test_Problem778(t *testing.T) {
+
+	qs := []question778{
+		question778{
+			para778{[][]int{[]int{0, 2}, []int{1, 3}}},
+			ans778{3},
+		},
+
+		question778{
+			para778{[][]int{[]int{0, 1, 2, 3, 4}, []int{24, 23, 22, 21, 5}, []int{12, 13, 14, 15, 16}, []int{11, 17, 18, 19, 20}, []int{10, 9, 8, 7, 6}}},
+			ans778{16},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 778------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans778, q.para778
+		fmt.Printf("【input】:%v       【output】:%v\n", p, swimInWater(p.grid))
+	}
+	fmt.Printf("\n\n\n")
+}