题解 | #放苹果#

#include <iostream>
#include <vector>
using namespace std;

int countWays(int m, int n)
{
    std::vector<std::vector<int>> dp(n+1, std::vector<int>(m + 1, 0));
    for (int i = 1; i <= n; ++i)
    {
        dp[i][0] = 1;
        dp[i][1] = 1;
    }
     for (int i = 1; i <= m; ++i) {
         dp[1][i] = 1;
     }
    for (int i = 2; i <= n; ++i)
    {
        for (int j = 2; j <= m; ++j)
        {
            if (j < i)
            {
                dp[i][j] = dp[i - 1][j];
            }
            else
            {
                dp[i][j] = dp[i - 1][j] + dp[i][j - i];
            }
        }
    }
    return dp[n][m];
}


int main()
{
    int a, b;
    while (cin >> a >> b)
    { // 注意 while 处理多个 case
        cout << countWays(a, b) << endl;
    }
}
// 64 位输出请用 printf("%lld")

正确的思路好像不是这样，废了好久凑出来的