Question

我有以下代码：

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <iostream>
using namespace std;

#define N 2  /* # of thread */

int a[] = {10, 9, 8, 7, 6, 5, 4, 3, 2, 1};  /* target array */

/* structure for array index
 * used to keep low/high end of sub arrays
 */
typedef struct Arr {
    int low;
    int high;
} ArrayIndex;

void merge(int low, int high)
{
        int mid = (low+high)/2;
        int left = low;
        int right = mid+1;

        int b[high-low+1];
        int i, cur = 0;

        while(left <= mid && right <= high) {
                if (a[left] > a[right])
                        b[cur++] = a[right++];
                else
                        b[cur++] = a[right++];
        }

        while(left <= mid) b[cur++] = a[left++];
        while(right <= high) b[cur++] = a[left++];
        for (i = 0; i < (high-low+1) ; i++) a[low+i] = b[i];
}

void * mergesort(void *a)
{
        ArrayIndex *pa = (ArrayIndex *)a;
        int mid = (pa->low + pa->high)/2;

        ArrayIndex aIndex[N];
        pthread_t thread[N];

        aIndex[0].low = pa->low;
        aIndex[0].high = mid;

        aIndex[1].low = mid+1;
        aIndex[1].high = pa->high;

        if (pa->low >= pa->high) return 0;

        int i;
        for(i = 0; i < N; i++) pthread_create(&thread[i], NULL, mergesort, &aIndex[i]);
        for(i = 0; i < N; i++) pthread_join(thread[i], NULL);

        merge(pa->low, pa->high);

        //pthread_exit(NULL);
        return 0;
}

int main()
{
        ArrayIndex ai;
        ai.low = 0;
        ai.high = sizeof(a)/sizeof(a[0])-1;
        pthread_t thread;

        pthread_create(&thread, NULL, mergesort, &ai);
        pthread_join(thread, NULL);

        int i;
        for (i = 0; i < 10; i++) printf ("%d ", a[i]);
        cout << endl;

        return 0;
}

代码正在运行。但我需要一些帮助。我需要知道如何向用户询问数组a[]的大小并随机创建数组。我非常感谢你的帮助。感谢先进，对不起英语不好意思。

Answer 1

您为此目的使用vector。一个例子：

#include <vector>
...

std::vector<int> myarr;  //Note: No size is specified.
myarr.push_back(10);     //inserting an element at end of myarr
myarr.push_back(11);     //inserting another
std::cout<<myarr.size(); //number of element
//You can keep doing these things.

用户定义的数组大小

1 个答案: