算法第十四周作业01

Description

Given an unsorted array of integers, find the length of the longest consecutive elements sequence.

For example,

Given [100, 4, 200, 1, 3, 2],

The longest consecutive elements sequence is [1, 2, 3, 4]. Return its length: 4.

Your algorithm should run in O(n) complexity.

Solution

首先对输入数组排序

count表示局部有续子串长度，result表示最大有序子串长度（即返回的结果）

逐个迭代，当nums[i] == nums[i-1] + 1时，count++；当nums[i] == nums[i-1]时，跳过，不处理；否则，nums[i]和nums[i-1]不连续且不相等，则局部有序终止了，重置count。

Code

import java.util.Arrays;

public class Solution {
public int longestConsecutive(int[] nums) {
// 初始化
int result = nums.length == 0 ? 0 : 1;
int count = 1;
// 排序
Arrays.sort(nums);
// 逐个迭代判断
for (int i = 0; i < nums.length - 1; i++) {
if (nums[i + 1] == nums[i]+1) {
// 计数器加1
count++;
if (result < count)
result = count;
} else if(nums[i+1] != nums[i]) {
// 重置计数器
count = 1;
}
}
return result;
}
}