How to count elements of array in c++

问题

I have an array with a particular size (100 for example), which is filled with user input. However, the user might not necessarily enter enough data to fill the entire array.

I want to count the elements of the array which the user entered. How can I do this?

I tried by this for loop:

int COUNT=0;
for( int i=0; i<size; i++)
    if (Student[i]=1) //which means this element is true, not empty element.
        COUNT++;
cout<< COUNT+1 << "\n";

But this code gives an error on this line:

if (Students[i]==1)

Also, if the user enters repeated elements, I just want to count the unique elements (count each value one time).

My code is:

#include <iostream>
#include <string>
#include <sstream>
#include <math.h>
#define size 100
using namespace std;
int main()
{
    string Students_;
    string word2;

    getline(cin, Students_);
    int k;
    int l;
    k = Students_.find("[");
    Students_.erase(0, k + 1);
    l = Students_.find("]");
    string line2 = Students_.erase(l);
    stringstream iss(line2);
    string Students[size];
    int counter = 0;
    while (getline(iss, word2, ';') && counter < size) {
        Students[counter++] = word2;
    }

    int COUNT = 0;
    for (int i = 0; i < size; i++)
        if (Students[i] == 1)
            COUNT++;
    cout << COUNT + 1 << "\n";
    return 0;
}

The input for example is:

Students=[8347,Islam Said,(ARC135,ARC114,ARC134,ARC135);8256,Esraa Said,(ARC134,ARC135,ARC114);8336,Ismail Said,(ARC134,ARC135,ARC114);8285,Ismail Adballah,(ARC114,ARC135,ARC134,ARC114);8349,Esraa Kassem,(ARC135,ARC114,ARC134);8505,Bassant Kassem,(ARC114,ARC135,ARC134,ARC114);8381,Ismail Kassem,(ARC135,ARC134,ARC114,ARC135);8360,Bassant AbdAlrahman,(ARC114);8498,Mohamed Kamal,(ARC135,ARC114,ARC134);8255,Ali Bassem,(ARC114,ARC135);8437,Mohamed Said,(ARC135);8524,Osama Adballah,(ARC114,ARC135);8334,Osama Kamal,(ARC114,ARC135,ARC134);8501,Esraa Tarek,(ARC135,ARC134);8394,Ahmed Zain,(ARC134,ARC135)]

The input is not constant, it's just an example.

回答1:

Within the if statement you're assigning a value instead of checking it.

Try

if (Student[i] == 1)

回答2:

Try sizeof(array)/sizeof(array[0])

In C++ always use std::vector. There are several inbuilt functions and an extended functionality.

std::vector has a method size() which returns the number of elements in the vector.

(Yes, this is tongue-in-cheek answer)

来源：https://stackoverflow.com/questions/37072735/how-to-count-elements-of-array-in-c