LeetCode First Missing Positive

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：给出一个数组，求其第一个缺失的整数

思路：从1开始查找，如果找到，就开始查找2，依次类推。在查找的过程中有两种情况

（1）如果nums[i] 不等于要找的数，i++

（2）如果相等，就将nums[i]与要找的数所在的下标交换，并且从要找的数的下标开始继续查找，同时将要查找的数加1

代码如下：

class Solution
{public int firstMissingPositive(int[] nums){int result = 1;for (int i = 0; i < nums.length;){if (nums[i] != result) i++;else{int tmp = nums[result - 1];nums[result - 1] = nums[i];nums[i] = tmp;i = result++;}}return result;}
}

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