p41

发表于 | 分类于 |

LeetCode 41 First Missing Positive 题解

1.题目：

Given an unsorted integer array, find the first missing positive integer.
For example,
Given [1,2,0] return 3,
and [3,4,-1,1] return 2.

Your algorithm should run in O(n) time and uses constant space.

题意：

输入一个数组，返回它所不包含的最小的正数。

2.解题思路:

桶装

3.代码

[title] [] [url] [link text]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
 

public class Solution {
    public int firstMissingPositive(int[] nums) {
        int max = 0;
		for (int i = 0; i < nums.length; i++) {
			if (nums[i] > max)
				max = nums[i];
		}
		max = max + 1;
		int[] a = new int[max];
		for (int i = 0; i < nums.length; i++) {
			if (nums[i] > 0)
				a[nums[i]]++;
		}
		for (int i = 1; i < max; i++) {

			if (a[i] == 0)
				return i;
		}
		return max;
    }
}

4.一些总结：