update solution 0031 & 0048

leetcode/0031.Next-Permutation/31. Next Permutation.go

@@ -1,14 +1,43 @@
-// https://leetcode.com/problems/next-permutation/discuss/1554932/Go-Submission-with-Explanation
-// Time O(N) , Space: O(1)
-
 package leetcode
 
-// [2,(3),6,5,4,1] -> 2,(4),6,5,(3),1 -> 2,4, 1,3,5,6
+// 解法一
 func nextPermutation(nums []int) {
+	i, j := 0, 0
+	for i = len(nums) - 2; i >= 0; i-- {
+		if nums[i] < nums[i+1] {
+			break
+		}
+	}
+	if i >= 0 {
+		for j = len(nums) - 1; j > i; j-- {
+			if nums[j] > nums[i] {
+				break
+			}
+		}
+		swap(&nums, i, j)
+	}
+	reverse(&nums, i+1, len(nums)-1)
+}
+
+func reverse(nums *[]int, i, j int) {
+	for i < j {
+		swap(nums, i, j)
+		i++
+		j--
+	}
+}
+
+func swap(nums *[]int, i, j int) {
+	(*nums)[i], (*nums)[j] = (*nums)[j], (*nums)[i]
+}
+
+// 解法二
+// [2,(3),6,5,4,1] -> 2,(4),6,5,(3),1 -> 2,4, 1,3,5,6
+func nextPermutation1(nums []int) {
 	var n = len(nums)
 	var pIdx = checkPermutationPossibility(nums)
 	if pIdx == -1 {
-		reverse(nums, 0, n-1)
+		reverse(&nums, 0, n-1)
 		return
 	}
 
@@ -16,26 +45,14 @@ func nextPermutation(nums []int) {
 	// start from right most to leftward,find the first number which is larger than PIVOT
 	for rp > 0 {
 		if nums[rp] > nums[pIdx] {
-			swap(nums, pIdx, rp)
+			swap(&nums, pIdx, rp)
 			break
 		} else {
 			rp--
 		}
 	}
 	// Finally, Reverse all elements which are right from pivot
-	reverse(nums, pIdx+1, n-1)
-}
-
-func swap(nums []int, i, j int) {
-	nums[i], nums[j] = nums[j], nums[i]
-}
-
-func reverse(nums []int, s int, e int) {
-	for s < e {
-		swap(nums, s, e)
-		s++
-		e--
-	}
+	reverse(&nums, pIdx+1, n-1)
 }
 
 // checkPermutationPossibility returns 1st occurrence Index where

leetcode/0048.Rotate-Image/48. Rotate Image.go

@@ -1,8 +1,24 @@
-// Time: O(N) Space: O(1)
-
 package leetcode
 
+// 解法一
 func rotate(matrix [][]int) {
+	length := len(matrix)
+	// rotate by diagonal 对角线变换
+	for i := 0; i < length; i++ {
+		for j := i + 1; j < length; j++ {
+			matrix[i][j], matrix[j][i] = matrix[j][i], matrix[i][j]
+		}
+	}
+	// rotate by vertical centerline 竖直轴对称翻转
+	for i := 0; i < length; i++ {
+		for j := 0; j < length/2; j++ {
+			matrix[i][j], matrix[i][length-j-1] = matrix[i][length-j-1], matrix[i][j]
+		}
+	}
+}
+
+// 解法二
+func rotate1(matrix [][]int) {
 	n := len(matrix)
 	if n == 1 {
 		return