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MinimumCostForTickets.cpp
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MinimumCostForTickets.cpp
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// https://leetcode.com/problems/minimum-cost-for-tickets/description/
class Solution {
public:
// Simple Recursive Solution
// int solve(int n, vector<int> &days, vector<int> &costs, int index){
// if(index>=n)
// return 0;
// int option1= costs[0] + solve(n, days, costs, index+1);
// int i=0;
// for(i= index; i<n && days[i]<days[index]+7; i++);
// int option2= costs[1] + solve(n, days, costs, i);
// for(i= index; i<n && days[i]<days[index]+30; i++);
// int option3= costs[2] + solve(n, days, costs, i);
// return min(option1, min(option2, option3));
// }
// Recursion + Memoization (Top-Down Approach)
// int solve(int n, vector<int> &days, vector<int> &costs, int index, vector<int> &dp){
// if(index>=n)
// return 0;
// if(dp[index]!=-1)
// return dp[index];
// int option1= costs[0] + solve(n, days, costs, index+1, dp);
// int i=0;
// for(i= index; i<n && days[i]<days[index]+7; i++);
// int option2= costs[1] + solve(n, days, costs, i, dp);
// for(i= index; i<n && days[i]<days[index]+30; i++);
// int option3= costs[2] + solve(n, days, costs, i, dp);
// dp[index]= min(option1, min(option2, option3));
// return dp[index];
// }
// Tabulation Method (Bottom-Up Approach)
// int solve(int n, vector<int> &days, vector<int> &costs){
// vector<int> dp(n+1, INT_MAX);
// dp[n]= 0;
// for(int index=n-1; index>=0; index--){
// int option1= costs[0] + dp[index+1];
// int i=0;
// for(i= index; i<n && days[i]<days[index]+7; i++);
// int option2= costs[1] + dp[i];
// for(i= index; i<n && days[i]<days[index]+30; i++);
// int option3= costs[2] + dp[i];
// dp[index]= min(option1, min(option2, option3));
// }
// return dp[0];
// }
int mincostTickets(vector<int>& days, vector<int>& costs) {
// Simple Recursive Solution
// return solve(days.size(), days, costs, 0);
// Recursion + Memoization (Top-Down Approach)
// vector<int> dp(days.size()+1, -1);
// return solve(days.size(), days, costs, 0, dp);
// Tabulation Method (Bottom-Up Approach)
// return solve(days.size(), days, costs);
int ans= 0;
queue<pair<int, int>> weeks;
queue<pair<int, int>> monthly;
for(auto day: days){
while(!weeks.empty() && weeks.front().first+7 <=day )
weeks.pop();
while(!monthly.empty() && monthly.front().first+30 <=day )
monthly.pop();
weeks.push(make_pair(day, ans + costs[1]));
monthly.push(make_pair(day, ans + costs[2]));
ans= min(ans + costs[0], min(weeks.front().second, monthly.front().second));
}
return ans;
}
};