From f53e5114d60f58b0de1ef476cd6f89eeef5056fc Mon Sep 17 00:00:00 2001
From: YDZ <ydz627@gmail.com>
Date: Thu, 8 Aug 2019 21:59:04 +0800
Subject: [PATCH] =?UTF-8?q?=E6=B7=BB=E5=8A=A0=20problem=20990?=
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---
 ...0. Satisfiability of Equality Equations.go | 22 +++++++
 ...tisfiability of Equality Equations_test.go | 62 ++++++++++++++++++
 .../README.md                                 | 65 +++++++++++++++++++
 3 files changed, 149 insertions(+)
 create mode 100644 Algorithms/0990. Satisfiability of Equality Equations/990. Satisfiability of Equality Equations.go
 create mode 100644 Algorithms/0990. Satisfiability of Equality Equations/990. Satisfiability of Equality Equations_test.go
 create mode 100755 Algorithms/0990. Satisfiability of Equality Equations/README.md

diff --git a/Algorithms/0990. Satisfiability of Equality Equations/990. Satisfiability of Equality Equations.go b/Algorithms/0990. Satisfiability of Equality Equations/990. Satisfiability of Equality Equations.go
new file mode 100644
index 00000000..0ab59367
--- /dev/null
+++ b/Algorithms/0990. Satisfiability of Equality Equations/990. Satisfiability of Equality Equations.go	
@@ -0,0 +1,22 @@
+package leetcode
+
+func equationsPossible(equations []string) bool {
+	if len(equations) == 0 {
+		return false
+	}
+	uf := UnionFind{}
+	uf.init(26)
+	for _, equ := range equations {
+		if equ[1] == '=' && equ[2] == '=' {
+			uf.union(int(equ[0]-'a'), int(equ[3]-'a'))
+		}
+	}
+	for _, equ := range equations {
+		if equ[1] == '!' && equ[2] == '=' {
+			if uf.find(int(equ[0]-'a')) == uf.find(int(equ[3]-'a')) {
+				return false
+			}
+		}
+	}
+	return true
+}
diff --git a/Algorithms/0990. Satisfiability of Equality Equations/990. Satisfiability of Equality Equations_test.go b/Algorithms/0990. Satisfiability of Equality Equations/990. Satisfiability of Equality Equations_test.go
new file mode 100644
index 00000000..75b10c33
--- /dev/null
+++ b/Algorithms/0990. Satisfiability of Equality Equations/990. Satisfiability of Equality Equations_test.go	
@@ -0,0 +1,62 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question990 struct {
+	para990
+	ans990
+}
+
+// para 是参数
+// one 代表第一个参数
+type para990 struct {
+	a []string
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans990 struct {
+	one bool
+}
+
+func Test_Problem990(t *testing.T) {
+
+	qs := []question990{
+
+		question990{
+			para990{[]string{"a==b", "b!=a"}},
+			ans990{false},
+		},
+
+		question990{
+			para990{[]string{"b==a", "a==b"}},
+			ans990{true},
+		},
+
+		question990{
+			para990{[]string{"a==b", "b==c", "a==c"}},
+			ans990{true},
+		},
+
+		question990{
+			para990{[]string{"a==b", "b!=c", "c==a"}},
+			ans990{false},
+		},
+
+		question990{
+			para990{[]string{"c==c", "b==d", "x!=z"}},
+			ans990{true},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 990------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans990, q.para990
+		fmt.Printf("【input】:%v       【output】:%v\n", p, equationsPossible(p.a))
+	}
+	fmt.Printf("\n\n\n")
+}
diff --git a/Algorithms/0990. Satisfiability of Equality Equations/README.md b/Algorithms/0990. Satisfiability of Equality Equations/README.md
new file mode 100755
index 00000000..2d32532b
--- /dev/null
+++ b/Algorithms/0990. Satisfiability of Equality Equations/README.md	
@@ -0,0 +1,65 @@
+# [990. Satisfiability of Equality Equations](https://leetcode.com/problems/satisfiability-of-equality-equations/)
+
+
+## 题目:
+
+Given an array equations of strings that represent relationships between variables, each string `equations[i]` has length `4` and takes one of two different forms: `"a==b"` or `"a!=b"`. Here, `a` and `b` are lowercase letters (not necessarily different) that represent one-letter variable names.
+
+Return `true` if and only if it is possible to assign integers to variable names so as to satisfy all the given equations.
+
+**Example 1:**
+
+    Input: ["a==b","b!=a"]
+    Output: false
+    Explanation: If we assign say, a = 1 and b = 1, then the first equation is satisfied, but not the second.  There is no way to assign the variables to satisfy both equations.
+
+**Example 2:**
+
+    Input: ["b==a","a==b"]
+    Output: true
+    Explanation: We could assign a = 1 and b = 1 to satisfy both equations.
+
+**Example 3:**
+
+    Input: ["a==b","b==c","a==c"]
+    Output: true
+
+**Example 4:**
+
+    Input: ["a==b","b!=c","c==a"]
+    Output: false
+
+**Example 5:**
+
+    Input: ["c==c","b==d","x!=z"]
+    Output: true
+
+**Note:**
+
+1. `1 <= equations.length <= 500`
+2. `equations[i].length == 4`
+3. `equations[i][0]` and `equations[i][3]` are lowercase letters
+4. `equations[i][1]` is either `'='` or `'!'`
+5. `equations[i][2]` is `'='`
+
+
+
+## 题目大意
+
+给定一个由表示变量之间关系的字符串方程组成的数组，每个字符串方程 equations[i] 的长度为 4，并采用两种不同的形式之一："a==b" 或 "a!=b"。在这里，a 和 b 是小写字母（不一定不同），表示单字母变量名。只有当可以将整数分配给变量名，以便满足所有给定的方程时才返回 true，否则返回 false。 
+
+提示：
+
+1. 1 <= equations.length <= 500
+2. equations[i].length == 4
+3. equations[i][0] 和 equations[i][3] 是小写字母
+4. equations[i][1] 要么是 '='，要么是 '!'
+5. equations[i][2] 是 '='
+
+
+
+## 解题思路
+
+
+- 给出一个字符串数组，数组里面给出的是一些字母的关系，只有 `'=='` 和 `'! ='` 两种关系。问给出的这些关系中是否存在悖论？
+- 这一题是简单的并查集的问题。先将所有 `'=='` 关系的字母 `union()` 起来，然后再一一查看 `'! ='` 关系中是否有 `'=='` 关系的组合，如果有，就返回 `false`，如果遍历完都没有找到，则返回 `true`。