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two_arrays.cpp
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168 lines (114 loc) · 2.65 KB
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#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
#include<bits/stdc++.h>
#include <algorithm>
#include <iostream>
#include <cstdio>
#include <queue>
#include <set>
#include <string>
#include <stdbool.h>
#include<ctime>
#include <cstring>
#define pub push_back
#define ll long long
#define max(a,b) ((a) > (b) ? (a) : (b))
#define min(a,b) ((a) < (b) ? (a) : (b))
#define BEND(c) (c).begin(),(c).end()
#define BEND2(c) (c).rbegin(),(c).rend()
#define fi first
#define se second
#define pi 3.1415926535897932384626
#define pfd(a) printf("%.15lf \n",a);
#define IOS ios_base::sync_with_stdio(false);cin.tie(0);
#define endl "\n"
#define MOD ( int)( 1e9 +7)
#define MAXN (ll) ((1000010))
#define ALPHABET_SIZE 26
//#define N (int)(1e5+10)
#define sag (sol|1)
#define sol (root<<1)
#define ort (bas+son)/2
#define INF (ll )1e18
#define int ll
#define findone(x) __builtin_popcount(x)
using namespace std;
typedef vector<int> vi;
typedef vector<bool> vb;
typedef vector<vector<int>> vvi;
typedef vector<vector<pair<int, int>>> vvpi;
typedef vector<long long> vl;
typedef vector<pair<int, int>> vpi;
typedef vector<pair<long long, long long>> vpl;
typedef pair<int, int> pii;
typedef pair <ll, ll> pll;
typedef vector<vi> graph;
ll tt=1 , n , m , x , k , res= 0 , ans =0 ;
ll fac[MAXN];
ll fast(ll a,ll b , ll mod )
{
ll res=1;
while(b)
{
if(b&1LL)
{
res*=a;
res%=mod;
}
b>>=1LL;
a*=a;
a%=mod;
}
return (res + mod)%mod;
}
void pre()
{
fac[0] = 1;
for (ll i = 1; i < 55; ++i)
fac[i] = (fac[i-1] * i) ;
}
int C(int a, int b)
{
if (a < b) return 0;
if (a == b) return 1;
int val = fac[a];
val = (val * fast(fac[b], MOD-2 , MOD)) % MOD;
val = (val * fast(fac[a-b], MOD-2 , MOD)) % MOD;
return (val +MOD)%MOD ;
}
int dp[23][1003][2];
;
void solve() {
cin >> n >>m ;
dp[0][0][0] = 1;
for (int i = 1; i <= m; i++) {
for (int j = 1; j <= n; j++) {
for (int k = 0; k <= j; k++) {
dp[i][j][0] = (dp[i][j][0] + dp[i - 1][k][0])%MOD;
}
}
}
dp[0][n + 1][1] = 1;
for (int i = 1; i <= m; i++) {
for (int j = 1; j <= n; j++) {
for (int k = n + 1; k >= j; k--) {
dp[i][j][1] = (dp[i][j][1] + dp[i - 1][k][1])%MOD;
}
}
}
ans = 0;
for (int i = 1; i <= n; i++) {
for (int j = i; j <= n; j++) {
ans = (ans + (dp[m][i][0] * dp[m][j][1]) %MOD )%MOD;
}
}
cout << ans % MOD<< endl;
}
signed main(){
IOS;
//cin >> tt;
while (tt--){
solve();
}
//getchar(); getchar();
return 0;