所需最少站臺數問題
現在的問題是,對於給定到達和離開時間,找出鐵路所需的最小站臺數(所有火車都不能等待)。
透過按順序對所有時間排序,我們很容易就能找到解決方案,這就便於跟蹤火車到達但尚未離開車站的時間。
此問題的以下時間複雜度為 O(n Log n)。
輸入和輸出
Input: Lists of arrival time and departure time. Arrival: {900, 940, 950, 1100, 1500, 1800} Departure: {910, 1200, 1120, 1130, 1900, 2000} Output: Minimum Number of Platforms Required: 3
演算法
minPlatform(arrival, departure, int n)
**輸入 −** 到達時間和離開時間的列表,以及列表中的專案數量
**輸出 −** 解決此問題的所需最小站臺數。
Begin sort arrival time list, and departure time list platform := 1 and minPlatform := 1 i := 1 and j := 0 for elements in arrival list ‘i’ and departure list ‘j’ do if arrival[i] < departure[j] then platform := platform + 1 i := i+1 if platform > minPlatform then minPlatform := platform else platform := platform – 1 j := j + 1 done return minPlatform End
示例
#include<iostream> #include<algorithm> using namespace std; int minPlatform(int arrival[], int departure[], int n) { sort(arrival, arrival+n); //sort arrival and departure times sort(departure, departure+n); int platform = 1, minPlatform = 1; int i = 1, j = 0; while (i < n && j < n) { if (arrival[i] < departure[j]) { platform++; //platform added i++; if (platform > minPlatform) //if platform value is greater, update minPlatform minPlatform = platform; } else { platform--; //delete platform j++; } } return minPlatform; } int main() { int arrival[] = {900, 940, 950, 1100, 1500, 1800}; int departure[] = {910, 1200, 1120, 1130, 1900, 2000}; int n = 6; cout << "Minimum Number of Platforms Required: " << minPlatform(arrival, departure, n); }
輸出
Minimum Number of Platforms Required: 3
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