CodeForces 543A - Writing Code DP 完全背包

/*************************************************************************
    > File Name: code03.cpp
    > Author: Jeremy Wu
    > Created Time: Sun 31 May 2015 02:37:07 PM CST
 ************************************************************************/

#include <iostream>

using namespace std;

const int N = 555;
int a[N];
int dp[2][N][N];

int main () {
    int i, j, k, l, m, n, bl, bugs, md;

    cin >> n >> bl >> bugs >> md;
    for (i = 0; i < n; ++i) cin >> a[i];
    dp[0][0][0] = 1;

    for (int it = 1; it <= n; ++it) {
        i = it & 1;
        for (j = 0; j <= bl; ++j) {
            for (k = 0; k <= bugs; ++k) {
                dp[i][j][k] = dp[i ^ 1][j][k];
                if (j > 0 && k >= a[it - 1]) {
                    dp[i][j][k] += dp[i][j - 1][k - a[it - 1]];
                }
                while (dp[i][j][k] >= md) {
                    dp[i][j][k] -= md;
                }
            }
        }
    }

    int ans = 0;
    for (i = 0; i <= bugs; ++i) {
        ans += dp[n & 1][bl][i];
        while (ans >= md) {
            ans -= md;
        }
    }
    cout << ans << endl;

    return 0;
}