public:

int utility(vector<int> &cost, int index, vector<int> &dp) {

if (index >= cost.size()) {

return 0;

}

if (dp[index] != -1) {

return dp[index];

}

int ostep = cost[index] + utility(cost, index + 1, dp);

int tstep = cost[index] + utility(cost, index + 2, dp);

return dp[index] = min(ostep, tstep);

}

int minCostClimbingStairs(vector<int> &cost) {

vector<int> dp(cost.size(), -1);

return min(utility(cost, 0, dp), utility(cost, 1, dp));

}