C++指針數學鬥爭

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我的代碼中的所有東西除了最後的數學運算外，都會輸出各種瘋狂的負數。任何建議來解決我混亂的代碼混亂？C++指針數學鬥爭

#include <iostream> 
using namespace std; 


double getScores(double *, int); 
int sort(double *, int); 
double calcAvg(double *, int);  //function prototypes 
void displayRpt(double *, int); 


int main() { 
    int size; 
    cout << "Welcome to Daniel Mikos' Quiz Score Calculator" << endl << endl; 
    cout << "How many test scores would you like to enter? ";    //prompt for # of test scores 
    cin >> size; 

    double *scores; //pointer for array 
    scores = new double[size]; //Declares a pointer to an array of doubles 
    getScores(scores, size); 
    sort(scores, size); 
    calcAvg(scores,size); 
    displayRpt(scores, size); 


    system("Pause"); 
    return 0; 
} 

double getScores(double *scores, int size) { //prompts for scores 

    while (size <= 0) { 
     cout << "Error! There must be at least one score!" << endl; 
     cout << "Please try again!" << endl; 
     cout << "Enter number of test scores you would like to process: "; 
     cin >> size; 
    } 

    //scores = new double[size]; 
    for (int i = 0; i < size; i++){ 
     cout << "Enter test score " << (i +1)<< ": ";     //prompt for each score 
     cin >> scores[i]; 
    } 

    delete scores; 
    return 0; 
} 

int sort(double *scores, int size) { //sorts array from largest to smallest 
    double temp; 
    for (int i = 1; i <= size; i++) { 
     for (int j = 0; j < size; j++) { 
      if (scores[j + 1] > scores[j]) { 
       temp = scores[j]; 
       scores[j] = scores[j + 1]; 
       scores[j + 1] = temp; 
      } 
     } 
    } 
    return *scores; 
} 

double calcAvg(double *scores, int size) { //calculates average test score 
    double average; 
    double total = 0; 

    for (int i = 0; i < size; i++) { 
     total = total + scores[i]; 

    } 

    average = total/size; 
    cout << endl <<"The average score: " << average <<endl <<endl; 
    return average; 
} 

void displayRpt(double *scores, int size) { //output report 
    for (int i = 1; i <= size; i++) { 
     cout << "Test score ("<< i <<"): "<<scores[i]<<endl; 
    } 

}

來源

2016-09-19 Mikos

多少/多大的數字？可能溢出 – user463035818

'displayRpt'在數組的末尾。 'sort'不符合你的期望。這聽起來像你可能需要學習如何使用調試器來遍歷代碼。使用一個好的調試器，您可以逐行執行您的程序，並查看它與您期望的偏離的位置。如果你打算做任何編程，這是一個重要的工具。進一步閱讀：** [如何調試小程序]（http://ericlippert.com/2014/03/05/how-to-debug-small-programs/）** – NathanOliver

該排序將有一些超出範圍訪問對於'[j + 1]'當'j'具有其最大值時。 –

在getScore你這樣做：

delete scores;

因爲你new []分配這是不確定的。

即使您正確地做到了這一點 - delete [] scores; - 它會釋放內存scores指向。
對該內存的任何後續訪問都是未定義的。

將取消分配移至main。

來源

2016-09-19 14:27:51 molbdnilo

C++指針數學鬥爭

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