Solution:
int minCost(vector<vector<int>> cost){
int result =0;
int r = cost.size();
for(int i=0; i<n; i++){
cost[i][0] += min(cost[i-1][1], cost[i-1][2]);
cost[i][1] += min(cost[i-1][0], cost[i-1][2]);
cost[i][2] += min(cost[i-1][1], cost[i-1][0]);
}
result = min(min(cost[r-1][0], cost[r-1][1]),cost[r-1][2]);
return result;
}