POJ 2229 Sumsets——完全背包

#include <cstdio>#include <cstring>#include <iostream>#include <algorithm>using namespace std;const int maxn = 1e6 + 5;const int mod = 1e9;int a[32], dp[maxn];int main() {    a[0] = 1;    for (int i = 1; i <= 20; i++) a[i] = a[i - 1] * 2;    dp[0] = 1;    for (int i = 0; i <= 20; i++) {        for (int j = a[i]; j < maxn; j++) {            dp[j] = (dp[j] + dp[j - a[i]]) % mod;        }    }    int n;    while (~scanf("%d", &n)) printf("%d\n", dp[n]);    return 0;}