First Missing Positive

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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.

#include<iostream>
#include<vector>
#include<algorithm>

using namespace std;

struct great_zero :public unary_function<int, bool>{
	bool operator()(int&x){ return x > 0; }
};
int firstMissingPositive(int A[], int n) {

	vector<int>T(A, A + n);
	if (T.empty())
		return 1;
	sort(T.begin(), T.end());
	auto iter = find_if(T.begin(), T.end(), great_zero());
	if (iter==T.end())
		return 1;
	int target = *iter;
	if (target > 1)
		return 1;
	for (; iter != T.end(); ++iter)
	{
		if (*iter - target>1)
			return target + 1;
		target = *iter;
	}
	return T.back() + 1;
}

def firstMissingPositive(A):
    if len(A)==0:
        return 1
    A.sort()
    posIdx = None
    target = None
    for index in range(len(A)):
        if A[index]>0:
            posIdx = index
            target = A[index]
            break
    else:
        return 1;
    if target > 1:
        return 1
    for index in range(posIdx+1,len(A)):
        if A[index]-target>1:
            return target+1
    return A[len(A)-1]+1

First Missing Positive

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原文地址：http://blog.csdn.net/li_chihang/article/details/44171523