[LeetCode] [First Missing Positive 2012-03-08]

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.

class
Solution {

public:

void
LinkMove(int
A[], int
i, int
n)

{

if(A[i] > n || A[i] <= 0)

{

A[i] = -1;

return;

}

if(A[i] == i+1) return;

int
s = A[i]-1;

int
tmp = A[s];

A[s] = A[i];

A[i] = tmp;

if(A[s] != A[i] ) //should be check, or there will be a circle call

{

LinkMove(A, i, n);

}

int
firstMissingPositive(int
A[], int
n) {

for(int
i = 0;i<n;i++)

{

LinkMove(A, i, n);

}

for(int
i = 0; i< n; i++)

{

if(A[i] <= 0 || A[i] != i+1) return
i+1;

}

return
n+1;

}

};

[LeetCode] [First Missing Positive 2012-03-08]

时间： 2024-08-05 10:01:55

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