蓝桥杯算法提高VIP-摆花 （C++代码）动态规划

解题思路:

F[i][j] 为用了前i种花，从左到右摆了j盆的方法数。

F[i][j] = F[i-1][j] + F[i][j-1] - F[i-1][j-ai-1]

F[i-1][j-ai-1] 转移到 F[i][j]需要摆ai+1盆花，所以需要减去

注意事项:

参考代码:

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <string>
#include <vector>
#include <queue>
using namespace std;
 
#define mod 1000007
 
const int maxn = 105;
int n, m;
int a[maxn];
int f[maxn][maxn];
 
int main() {
        cin >> n >> m;
        for (int i=1;i<=n;++i) cin >> a[i];
        memset(f, 0, sizeof(f));
        for (int i=0;i<=n;++i) f[i][0] = 1;
        for (int i=1;i<=n;++i)
            for (int j=1;j<=m;++j) {
                f[i][j] = f[i-1][j]+f[i][j-1];
                if (j - a[i] - 1 >= 0)
                    f[i][j] -= f[i-1][j-a[i]-1];
                f[i][j] = (f[i][j] + mod)%mod;
            }
        cout << f[n][m];
    return 0;
}