.\128.最长连续序列 ok map

侯利朋 · 侯利朋 · commit f8faa2650169 · 2019-09-02T13:48:41.000+08:00
diff --git a/128.最长连续序列-sort-nlogn.go b/128.最长连续序列-sort-nlogn.go
@@ -0,0 +1,34 @@
+import "sort"
+
+/*
+ * @lc app=leetcode.cn id=128 lang=golang
+ *
+ * [128] 最长连续序列
+ */
+//  8 ms, faster than 46.27%
+// 法1：排序后查找，O(nlogn),不满足题目要求
+func longestConsecutive(nums []int) int {
+	if len(nums) == 0 {
+		return 0
+	}
+	sort.Ints(nums)
+
+	curLen := 1
+	maxLen := 1
+	for i := 1; i < len(nums); i++ { // 从1开始计算
+		if nums[i] == nums[i-1] {
+			// 重复元素，计数不更新
+		} else if nums[i] == nums[i-1]+1 {
+			curLen++
+		} else {
+			if curLen > maxLen {
+				maxLen = curLen
+			}
+			curLen = 1
+		}
+	}
+	if curLen > maxLen { // 统计最后一段的长度
+		maxLen = curLen
+	}
+	return maxLen
+}
diff --git a/128.最长连续序列.go b/128.最长连续序列.go
@@ -0,0 +1,38 @@
+/*
+ * @lc app=leetcode.cn id=128 lang=golang
+ *
+ * [128] 最长连续序列
+ */
+//  4 ms, faster than 96.52%
+// 法1：排序后查找，O(nlogn),不满足题目要求
+// 法2： map缓存。下面是实现方式
+func longestConsecutive(nums []int) int {
+	if len(nums) == 0 || len(nums) == 1 {
+		return len(nums)
+	}
+
+	buf := make(map[int]bool, len(nums))
+	for i := 0; i < len(nums); i++ {
+		buf[nums[i]] = true
+	}
+
+	curLen := 0
+	maxLen := 1
+	for _, v := range nums {
+		if buf[v-1] { // 一定注意，此处是对v-1进行判断，如果不存在，表示v是一个序列的开始
+			continue
+		}
+		curLen = 0
+		for buf[v] {
+			v++
+			curLen++
+		}
+		if curLen > maxLen {
+			maxLen = curLen
+		}
+	}
+	if curLen > maxLen {
+		maxLen = curLen
+	}
+	return maxLen
+}
