[leetcode刷题系列]First Missing Positive

class Solution {
public:
int firstMissingPositive(int A[], int n) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
for(int i = 0; i < n; ++ i){
int now = i;
while(now >= 0 && now < n){
if(A[now] - 1 == now)
break;
int target = A[now] - 1;
if(target < 0 || target >= n || A[now] == A[target])
break;
swap(A[target], A[now]);
}
}
for(int i = 0; i < n; ++ i)
if(A[i] != i + 1)
return i + 1;
return n + 1;
}
};