为什么不能成功分配数组？

Question

这是我的代码：

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

int find_cross(char*, int, int, int);
void reduction(char*, char*, int, int);

int main(){
    int n;
    int m;
    cin >> n >> m;
    char *data = new char[n * m];
    for(int i = 0; i < n; i++){
        cin >> (data+i*m);
    }
    cout << "pass one" << endl;
    char *original = new char[n * m];
    cout << "pass two" << endl;
    for(int i = 0; i < n * m; i++){
        *(original+i) = *(data+i);
    }
    int biggest_size;
    if(n >= m){
        if(m % 2 == 0){
            biggest_size = m - 1;
        }else{
            biggest_size = m;
        }
    }else{
        if(n % 2 == 0){
            biggest_size = n - 1;
        }else{
            biggest_size = n;
        }
    }
    {
        int biggest = 0;
        for(int i = 1; i < biggest_size + 1; i = i + 2){
            reduction(data, original, n, m);
            if(find_cross(data, i, n, m)){
                for(int j = biggest_size; j >= 1; j = j - 2){
                    if(find_cross(data, j, n, m)){
                        if((i * 2 - 1) * (j * 2 - 1) > biggest){
                            biggest = (i * 2 - 1) * (j * 2 - 1);
                        }
                        break;
                    }
                }
            }
        }
        cout << biggest;
    }
    delete [] data;
    delete [] original;
    system("pause");
    return 0;
}

int find_cross(char* data, int size, int row, int column){
    for(int i = (size - 1) / 2; i < row - (size - 1) / 2; i++){
        for(int j = (size - 1) / 2; j < column - (size - 1) / 2; j++){
            int yes = 1;
            for(int k = 0; k < (size - 1) / 2 + 1; k++){
                if(*(data+(i+k)*column+j) != 'G' || *(data+(i-k)*column+j) != 'G' || *(data+i*column+j+k) != 'G' || *(data+i*column+j-k) != 'G'){
                    yes = 0;
                    break;
                }
            }
            if(yes == 1){
                for(int k = 0; k < (size - 1) / 2 + 1; k++){
                    *(data+(i-k)*column+j) = 'A';
                    *(data+(i+k)*column+j) = 'A';
                    *(data+i*column+j+k) = 'A';
                    *(data+i*column+j-k) = 'A';
                }
                return 1;
            }else if(i == row - (size - 1) / 2 - 1 && j == column - (size - 1) / 2 - 1){
                return 0;
            }
        }
    }
    return -1;
}

void reduction(char* data, char* original, int row, int column){
    for(int i = 0; i < row; i++){
        for(int j = 0; j < column; j++){
            *(data+i*column+j) = *(original+i*column+j);
        }
    }
}

这是我的输入：

14 12
GGGGGGGGGGGG
GGGGGGGGGGGG
BGBGGGBGBGBG
BGBGGGBGBGBG
GGGGGGGGGGGG
GGGGGGGGGGGG
GGGGGGGGGGGG
GGGGGGGGGGGG
BGBGGGBGBGBG
BGBGGGBGBGBG
BGBGGGBGBGBG
BGBGGGBGBGBG
GGGGGGGGGGGG
GGGGGGGGGGGG

执行结果：

14 12
GGGGGGGGGGGG
GGGGGGGGGGGG
BGBGGGBGBGBG
BGBGGGBGBGBG
GGGGGGGGGGGG
GGGGGGGGGGGG
GGGGGGGGGGGG
GGGGGGGGGGGG
BGBGGGBGBGBG
BGBGGGBGBGBG
BGBGGGBGBGBG
BGBGGGBGBGBG
GGGGGGGGGGGG
GGGGGGGGGGGG
pass one

--------------------------------
Process exited after 256.8 seconds with return value 3221226356

问题出现在char *original = new char[n * m];，无法成功执行，程序crash。但是有一个奇怪的事情发生了，数组char *data = new char[n * m];可以分配成功。发生了什么，以及如何解决这个问题？ Original picture

Answer 1

您忘记了读取字符串时添加的 nul 终止符。您的第二次分配失败，因为您通过越界写入损坏了堆。您的数组中还需要一个字节

char *data = new char[n * m + 1];

或者您可以做一些明智的事情并将其视为吸取的教训并使用字符串向量。

vector<string> data(n);
for(int i = 0; i < n; i++){
    cin >> data[i];
}
vector<string> original = data;

看看您的代码变得多么清晰和简单？