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;
}