2017Nowcoder Girl初赛重现赛 F 美丽的项链

题目链接

疯狂dp走一发 

dp[i][j]代表前i种取j个

#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<string.h>
#include<queue>
#include<stack>
#include<list>
#include<map>
#include<set>
#include<vector>
using namespace std;
typedef long long int ll;
const int maxn =1e5+5;
const int maxm=10000;
const int mod =1e9+7;
const int INF=0x3f3f3f3f;
const double eps=1e-8;
int n,m;
ll dp[25][120];
int main()
{
	scanf("%d%d",&n,&m);
	dp[0][0]=1ll;
	for(int i=1;i<=n;i++)
	{
		int l,r;scanf("%d%d",&l,&r);
		for(int j=0;j<=m;j++)
			for(int k=l;k<=r;k++)
				dp[i][j+k]+=dp[i-1][j];
	}
	printf("%lld\n",dp[n][m]);
    return 0;
}