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[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.
http://www.cnblogs.com/AnnieKim/archive/2013/04/21/3034631.html
1 public class Solution { 2 public int firstMissingPositive(int[] A) { 3 if(A==null||A.length==0) 4 return 1; 5 int n=A.length; 6 for(int i=0;i<n;){ 7 if((A[i]!=i+1)&&A[i]>=1&&A[i]<=A.length&&A[A[i]-1]!=A[i]){ 8 int temp=A[A[i]-1]; 9 A[A[i]-1]=A[i];10 A[i]=temp;11 }else{12 ++i;13 }14 }15 for(int i=0;i<A.length;++i){16 if(A[i]!=i+1)17 return i+1;18 }19 return A.length+1;20 }21 }
[Leetcode] First Missing Positive
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