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
        int x = 0;
        bool nfound=false;
        for (int i=0; i<n; i++) {
            if (A[i] == n) {
                nfound = true;
                break;
            }
        }
        for (int i=0; i<n; i++) {
            if (A[i] > 0) {
                x = A[i];
                break;
            }
        }
        if (x==0) {
            return 1;
        }
        for (int i=0; i<n; i++) {
            if (A[i]<=0) {
                A[i] = x;
            }
        }
        for (int i=0; i<n; i++) {
            if (abs(A[i])<n && A[abs(A[i])]>0) {
                A[abs(A[i])] = -A[abs(A[i])];
            }
        }
        for (int i=1; i<n; i++) {
            if (A[i]>0) {
                return i;
            }
        }
        return n+nfound;
    }
};