5.7.cpp

#include <iostream>
#include <cstring>
using namespace std;

int fetch(int a[], int i, int j){
    return (a[i] >> j) & 1;  //return 0/1
}
int get(int a[], int i){
    int ret = 0;
    for(int j=31; j>=0; --j)
        ret = (ret << 1) | fetch(a, i, j);
    return ret;
}
int missing(int a[], int n){
    bool *b = new bool[n+1];
    memset(b, false, (n+1)*sizeof(bool));
    for(int i=0; i<n; ++i)
        b[get(a, i)] = true;
    for(int i=0; i<n+1; ++i){
        if(!b[i]) return i;
    }
    delete[] b;
}
int fetch1(int a[], int j){
    return (a[j/32] >> (j % 32)) & 1;
}
int get1(int a[], int i){
    int ret = 0;
    int base = 32*i;
    for(int j=base+31; j>=base; --j)
        ret = (ret << 1) | fetch1(a, j);
    return ret;
}
int missing1(int a[], int n){
    bool *b = new bool[n+1];
    memset(b, false, (n+1)*sizeof(bool));
    for(int i=0; i<n; ++i)
        b[get1(a, i)] = true;
    for(int i=0; i<n+1; ++i){
        if(!b[i]) return i;
    }
}

int main(){
    int a[] = {
        0, 1, 2, 3, 4, 5, 7, 8, 9, 10
    };
    cout<<missing(a, 10)<<endl;
    cout<<missing1(a, 10)<<endl;
    return 0;
}