D. Red-Green Towers Dp

题意：有两种颜色的积木 向上垒，每层只能是同一种颜色，且每层的个数等于层数。问有多少种垒法。

Dp滚动数组搞下就好了。

#include <cstdio>

#include <cstring>

#include <algorithm>

#include <climits>

#include <string>

#include <iostream>

#include <map>

#include <cstdlib>

#include <list>

#include <set>

#include <queue>

#include <stack>

#include <math.h>

using namespace std;

typedef long long LL;

const int mod = 1000000000 + 7;

const int  maxn = 2 * 100000 + 2;

int dp[10][maxn];

int main()

{

    int r, g;

    cin >> r >> g;

    int h = (int)sqrt((r + g) * 2);

    dp[0][0] = 1;

    for (int i = 1; i <= h; i++){

        for (int j = 0; j <= r; j++){

            int ans1 = 0; int ans2 = 0;int gg = i % 2;

            if (j >= i) ans1 = dp[gg ^ 1][j - i];

            int g1 = (i*(i - 1) / 2 - j);

            g1 = g - g1;

            if (g1 >= i) ans2 = dp[gg ^ 1][j];

            ans1 %= mod; ans2 %= mod;

            dp[i % 2][j] = ans1 + ans2; dp[i % 2][j] %= mod;

        }

    }

    int flag = 0; int sum = 0;

    for (int i = h; i >= 1; i--){

        for (int j = 0; j <= r; j++){

            if (dp[i % 2][j]) flag = 1;

            sum += dp[i % 2][j]; sum %= mod;

        }

        if (flag) break;

    }

    printf("%d\n", sum);

    return 0;

}