操作系統 短進程優先算法（C++）

思路

用結構體數組存儲pcb表，用優先隊列維護就緒的進程，優先隊列存儲pair<pcb的序號, 進程運行所需時間>，按照運行時間從小到大排序。然後運行即可。

例子

代碼

#include <iostream>
#include <algorithm>
#include <vector>
#include <map>
#include <string>
#include <string.h>
#include <cstdio>
#include <cstdlib>
#include <queue>
using namespace std;

#define MP(a,b) make_pair(a, b)
typedef pair<int, int> P;///pcb中的序號 服務時間

const int maxn_program = 1e5 + 10;
const int maxn_name = 1e2 + 10;

int N;              ///進程數目
int now_time;       ///現在的時間

struct node{
    char program_name[maxn_name];       ///進程名
    int arrive_time;                    ///到達時間
    int run_time;                       ///服務時間
    int finished_time;                  ///完成時間
    int wait_time;                      ///週轉時間
    double with_value_wait_time;        ///帶權週轉時間
    char status = 'W';     ///進程狀態(W,R,F)
}program[maxn_program];

bool cmp(node a, node b){
    if(a.arrive_time == b.arrive_time)
        return a.run_time < b.run_time;
    return a.arrive_time < b.arrive_time;
}

struct cmp2{
    template<typename T, typename U>
    bool operator()(T const& left, U const &right) {
        if (left.second > right.second)
            return true;
        return false;
    }
};

priority_queue <P, vector<P>, cmp2> que;

void out_put(){
    printf("now_time:%d\n", now_time);
    printf("%10s %10s %10s %10s %10s %10s %10s\n", "進程名", "到達時間", "服務時間", "完成時間", "週轉時間", "帶權週轉時間", "進程狀態");
    for(int i = 1; i <= N; i++){
        printf("%10s %10d %10d %10d %10d %10.2f %10c\n", program[i].program_name, program[i].arrive_time, program[i].run_time, program[i].finished_time, program[i].wait_time, program[i].with_value_wait_time, program[i].status);
    }
}

void run_it(){
    int pos = que.top().first;
    now_time += que.top().second;
    program[pos].finished_time = now_time;
    program[pos].status = 'F';
    program[pos].wait_time = now_time - program[pos].arrive_time;
    program[pos].with_value_wait_time = (double)program[pos].wait_time / program[pos].run_time;
    que.pop();
}

int main(){
    printf("輸入進程數目：");
    scanf("%d", &N);
    printf("依次輸入各進程的進程名、到達時間、服務時間：");
    for(int i = 1; i <= N; i++){
        scanf("%s %d %d", &program[i].program_name, &program[i].arrive_time, &program[i].run_time);
    }
    ///按到達時間排序,同時到達按照運行時間從短到長排序
    sort(program + 1, program + 1 + N, cmp);
    ///out_put();      ///輸出pcb
    for(int pos = 1; pos <= N;){
        while(pos <= N && program[pos].arrive_time <= now_time){
            que.push(MP(pos, program[pos].run_time));///壓入就緒隊列
            pos++;
        }
        if(!que.empty())///如果que不爲空
            run_it();///執行一個進程
        out_put();
    }
    while(!que.empty()){
        run_it();
        out_put();///輸出pcb
    }
    return 0;
}
/*
5
A 0 4
B 1 3
C 2 5
D 3 2
E 4 4
*/