规范格式

leetcode/0996.Number-of-Squareful-Arrays/996. Number of Squareful Arrays.go

@@ -0,0 +1,58 @@
+package leetcode
+
+import (
+	"math"
+	"sort"
+)
+
+func numSquarefulPerms(A []int) int {
+	if len(A) == 0 {
+		return 0
+	}
+	used, p, res := make([]bool, len(A)), []int{}, [][]int{}
+	sort.Ints(A) // 这里是去重的关键逻辑
+	generatePermutation996(A, 0, p, &res, &used)
+	return len(res)
+}
+
+func generatePermutation996(nums []int, index int, p []int, res *[][]int, used *[]bool) {
+	if index == len(nums) {
+		checkSquareful := true
+		for i := 0; i < len(p)-1; i++ {
+			if !checkSquare(p[i] + p[i+1]) {
+				checkSquareful = false
+				break
+			}
+		}
+		if checkSquareful {
+			temp := make([]int, len(p))
+			copy(temp, p)
+			*res = append(*res, temp)
+		}
+		return
+	}
+	for i := 0; i < len(nums); i++ {
+		if !(*used)[i] {
+			if i > 0 && nums[i] == nums[i-1] && !(*used)[i-1] { // 这里是去重的关键逻辑
+				continue
+			}
+			if len(p) > 0 && !checkSquare(nums[i]+p[len(p)-1]) { // 关键的剪枝条件
+				continue
+			}
+			(*used)[i] = true
+			p = append(p, nums[i])
+			generatePermutation996(nums, index+1, p, res, used)
+			p = p[:len(p)-1]
+			(*used)[i] = false
+		}
+	}
+	return
+}
+
+func checkSquare(num int) bool {
+	tmp := math.Sqrt(float64(num))
+	if int(tmp)*int(tmp) == num {
+		return true
+	}
+	return false
+}

leetcode/0996.Number-of-Squareful-Arrays/996. Number of Squareful Arrays_test.go

@@ -0,0 +1,57 @@
+package leetcode
+
+import (
+	"fmt"
+	"testing"
+)
+
+type question996 struct {
+	para996
+	ans996
+}
+
+// para 是参数
+// one 代表第一个参数
+type para996 struct {
+	one []int
+}
+
+// ans 是答案
+// one 代表第一个答案
+type ans996 struct {
+	one int
+}
+
+func Test_Problem996(t *testing.T) {
+
+	qs := []question996{
+
+		question996{
+			para996{[]int{1, 17, 8}},
+			ans996{2},
+		},
+
+		question996{
+			para996{[]int{1}},
+			ans996{1},
+		},
+
+		question996{
+			para996{[]int{2, 2, 2}},
+			ans996{1},
+		},
+
+		question996{
+			para996{[]int{51768, 47861, 48143, 33221, 50893, 56758, 39946, 10312, 20276, 40616, 43633}},
+			ans996{1},
+		},
+	}
+
+	fmt.Printf("------------------------Leetcode Problem 996------------------------\n")
+
+	for _, q := range qs {
+		_, p := q.ans996, q.para996
+		fmt.Printf("【input】:%v       【output】:%v\n", p, numSquarefulPerms(p.one))
+	}
+	fmt.Printf("\n\n\n")
+}

leetcode/0996.Number-of-Squareful-Arrays/README.md

@@ -0,0 +1,41 @@
+# [996. Number of Squareful Arrays](https://leetcode.com/problems/number-of-squareful-arrays/)
+
+
+
+## 题目
+
+Given an array `A` of non-negative integers, the array is *squareful* if for every pair of adjacent elements, their sum is a perfect square.
+
+Return the number of permutations of A that are squareful. Two permutations `A1` and `A2` differ if and only if there is some index `i` such that `A1[i] != A2[i]`.
+
+**Example 1:**
+
+    Input: [1,17,8]
+    Output: 2
+    Explanation: 
+    [1,8,17] and [17,8,1] are the valid permutations.
+
+**Example 2:**
+
+    Input: [2,2,2]
+    Output: 1
+
+**Note:**
+
+1. `1 <= A.length <= 12`
+2. `0 <= A[i] <= 1e9`
+
+
+## 题目大意
+
+给定一个非负整数数组 A，如果该数组每对相邻元素之和是一个完全平方数，则称这一数组为正方形数组。
+
+返回 A 的正方形排列的数目。两个排列 A1 和 A2 不同的充要条件是存在某个索引 i，使得 A1[i] != A2[i]。
+
+
+
+## 解题思路
+
+
+- 这一题是第 47 题的加强版。第 47 题要求求出一个数组的所有不重复的排列。这一题要求求出一个数组的所有不重复，且相邻两个数字之和都为完全平方数的排列。
+- 思路和第 47 题完全一致，只不过增加判断相邻两个数字之和为完全平方数的判断，注意在 DFS 的过程中，需要剪枝，否则时间复杂度很高，会超时。