k数和

class Solution {
public:
/**
* @param A: an integer array.
* @param k: a positive integer (k <= length(A))
* @param target: a integer
* @return an integer
*/
int kSum(vector<int> A, int k, int target) {
// wirte your code here
int n = A.size();
int buf[n+1][k+1][target+1];
for (int i = 0; i < n+1; i++)
{
for (int j = 0; j < k+1; j++)
{
for (int m = 0; m < target+1; m++)
{
if (j == 0 && m == 0)
{
buf[i][j][m] = 1;
}
else if (!(i == 0 || j == 0 || m == 0))
{
buf[i][j][m] = buf[i-1][j][m];
if (A[i-1] <= m)
{
buf[i][j][m] += buf[i-1][j-1][m-A[i-1]];
}
}
else
{
buf[i][j][m] = 0;
}
}
}
}

return buf
[k][target];
}
};