I am solving this problem (https://leetcode.com/problems/minimum-cost-to-merge-stones/).

The solution uses 3-D dp with following transitions:-

1) dp[i][j][m] means the cost needed to merge stone[i] ~ stones[j] into m piles.

Initial status dp[i][i][1] = 0 and dp[i][i][m] = infinity.

2) dp[i][j][m] = min(dp[i][mid][1] + dp[mid + 1][j][m — 1])

I am not able to understand the 2nd transition properly. Why are we trying to merge stones i~mid into only 1 stone and not considering other possibilities ? Shouldn't the transition be dp[i][j][m]=min(dp[i][mid][x]+dp[mid+1][j][m-x]) for x in range(1,m-1) ?

Thanks.