《深刻理解C指針》第四章 指針和數組

2019-12-01

19:07:20

 

 

 

 

 

 

 

 

 

 

 

 

#include <bits/stdc++.h>
#include <stdlib.h>
#include <stdio.h>
using namespace std;
#define maxn 10005
#define M 105
char *getLine(void){
    const size_t sizeIncrement = 10;
    char* buffer = (char*)malloc(sizeIncrement);
    printf("%d\n",buffer);
    char* currentPosition = buffer;
    size_t maximumLength = sizeIncrement;
    size_t length = 0;
    int character;
    if(currentPosition ==NULL){
        return NULL;
    }
    while(1){
        character = fgetc(stdin);
        if(character == '\n'){
            break;
        }
        if(++length >= maximumLength){
            char *newBuffer = (char*)realloc(buffer,maximumLength += sizeIncrement);
            printf("%d\n",newBuffer);
            if(newBuffer == NULL){
                free(buffer);
                return NULL;
            }
            currentPosition = newBuffer +(currentPosition - buffer);
            buffer = newBuffer;
        }
        *currentPosition++ = character;
        printf("%d\n",currentPosition);
    }
    *currentPosition = '\0';
    return buffer;
}
int main(){
    getLine();
    system("pause");
    return 0;
}

 

 

 能夠看出realloc後返回的仍是一開始的地址：10882360

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

#include <bits/stdc++.h>
#include <stdlib.h>
#include <stdio.h>
using namespace std;
#define maxn 10005
#define M 105

int main(){
    int* arr[5];
    for(int i=0;i<5;++i){
        *(arr+i) = (int*)malloc(sizeof(int));
        **(arr+i) = i;
        printf("%d\n",**(arr+i));
    }
    system("pause");
    return 0;
} 

 

 

---

 

 

 

 

#include <bits/stdc++.h>
#include <stdlib.h>
#include <stdio.h>
using namespace std;
#define maxn 10005
#define M 105

int main(){
    int matrix[2][5] = {{1,2,3,4,5},{6,7,8,9,10}};
    for(int i=0;i<2;++i){
        for(int j=0;j<5;++j){
            printf("matrix[%d][%d] Address: %p Value: %d\n",
            i,j,&matrix[i][j],matrix[i][j]);
        }
    }
    system("pause");
    return 0;
} 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

#include <bits/stdc++.h>
#include <stdlib.h>
#include <stdio.h>
using namespace std;
#define maxn 10005
#define M 105

int main(){
    char command[16];
    printf("Enter a Command: ");
    scanf("%s",command);
    if(strcmp(command,"Quit")==0){
        printf("The command was Quit");
    }else{
        printf("The command was not Quit");
    }
    system("pause");
    return 0;
} 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

#include <bits/stdc++.h>
#include <stdlib.h>
#include <stdio.h>
using namespace std;
#define maxn 10005
#define M 105

int main(){
    char* error = "ERROR: ";
    char* errorMessage = "Not enought memory";
    char* buffer = (char*)malloc(strlen(error)+strlen(errorMessage)+1);
    strcpy(buffer,error);
    strcat(buffer,errorMessage);
    printf("%s\n",buffer);
    printf("%s\n",error);
    printf("%s\n",errorMessage);
    system("pause");
    return 0;
}