C ++（线性搜索和排序）

Question

Help with C++. Two things that I am struggling with

1. I am trying to do a linear search of name of list but for some reason the message "ABSENT!" will not come up when I type in the wrong name. How do I fix that?

2. I am trying to sort the entered name alphabetically in ascending order by their last name but I don't really know how to use that for loop and array for that.

Below is what I have for coding so far (Where it says Linear Search and Sorting is where I need help and that needs to be revised).

#include <iostream>
#include <string>
#include <iomanip>
using namespace std;

const int Students = 10;
int numStudents = 0;
string StudentName[Students];
int found = -1;
string SearchName;

int main() {
        cout << "Enter the number of students (1-10): ";
        cin >> numStudents;

    for (int i = 0; i < numStudents; i++) {
        cout << "Enter a name: ";
        cin.ignore();
        getline(cin, StudentName[i]);
    }

    cout << "\nEnter a search name: ";
    cin.ignore();
    getline(cin, SearchName);

    **//Linear Search
    for (int i = 0; i < numStudents; i++) {

        if (StudentName[i] == SearchName)
            found = i;
            cout << "PRESENT! Found in position " << found << endl;

        if (StudentName[i] != SearchName)
                found = 0;
                cout << "ABSENT!" << endl;
    }
    //Sorting
    for (int i = 0; i < numStudents - 1; i++) {
        for (int j = i + 1; j < numStudents; j++)
            if (StudentName[i] > StudentName[j]) {
                string t = StudentName[i];
                StudentName[i] = StudentName[j];
                StudentName[j] = t;
            }
    }
    cout << "\nThe Sorted list is:" << "\n";**


    system("pause");
    return 0;
}

Answer 1

This code

    if (StudentName[i] == SearchName)
        found = i;
        cout << "PRESENT! Found in position " << found << endl;

    if (StudentName[i] != SearchName)
            found = 0;
            cout << "ABSENT!" << endl;

is missing braces for the if statements. It should be

    if (StudentName[i] == SearchName) {
        found = i;
        cout << "PRESENT! Found in position " << found << endl;
    }

    if (StudentName[i] != SearchName) {
            found = 0;
            cout << "ABSENT!" << endl;
    }

However the code is still not right because you cannot know that you haven't found a name until you have checked all the names. So logically the test for 'not found' can only go after the for loop.

I would write the code something like this

//Linear Search
found = -1;
for (int i = 0; i < numStudents; i++) {

    if (StudentName[i] == SearchName) {
        found = i;
        break; // we've found it, quit the loop
    }

}

if (found == -1) // did we find it?
    cout << "ABSENT!" << endl;
else
    cout << "PRESENT! Found in position " << found << endl;