动态分配二维数组

来源：互联网发布：心内事无人知蔡秋凤编辑：程序博客网时间：2024/06/10 18:25

为二维数组动态分配内存涉及以下两个问题：

数组元素是否需要连续
数组是否规则

在这里我们暂时不考虑数组是否规则，我们从数组元素的分配是否连续考虑。

已知第二维

    // 数组指针    char (*a1)[COLUMNS];    a1 = (char(*)[COLUMNS])calloc(ROWS,sizeof(char*));

已知第一维

    // 指针数组    char *a2[ROWS];    for(int i = 0; i < ROWS; i++) {        a2[i] = (char*)calloc(COLUMNS, sizeof(char));    }

已知第一维，一次分配内存（保证内存分配的连续性）

    // 指针数组    char *a3[ROWS];    a3[0] = (char *)calloc(ROWS*COLUMNS, sizeof(char));    for(int i = 1; i < ROWS; i++) {        a3[i] = a3[i-1] + COLUMNS;    }

两维都未知

    // 二级指针    char **a4;    a4 = (char **)calloc(ROWS, sizeof(char*));    for(int i = 0; i < ROWS; i++) {        a4[i] = (char*)calloc(COLUMNS, sizeof(char));    }

两维都未知，一次分配内存（保证内存分配的连续性）

    // 二级指针    char **a5;    a5 = (char**)calloc(ROWS, sizeof(char*));    a5[0] = (char*)calloc(ROWS*COLUMNS, sizeof(char));    for(int i = 1; i < ROWS; i++) {        a5[i] = a5[i-1] + COLUMNS;    }

完整代码

/* * 二维数组的动态内存分配 * 测试指针和数组之间的关系 */#include <stdio.h>#include <stdlib.h>#define ROWS 6#define COLUMNS 5#define P(a) \        { \            printf("sizeof(%s):\t%d\n",#a, (sizeof((a)))); \            printf("sizeof(%s[0]):\t%d\n",#a,(sizeof((a)[0]))); \        }#define OUT(a) \        {        \         printf("%s:\t  addr:%p\n",(#a),(a)); \         for(int i = 0; i < ROWS; i++){ \            printf("%s[%d]:\t  addr:%p\n",#a,i,((a)[i])); \         } \         for(int i = 0; i < ROWS; i++){ \            for(int j = 0; j < COLUMNS; j++){ \                printf("%s[%d][%d]: addr:%p\t",(#a),i,j,&a[i][j]);\            } \            printf("\n"); \         } \        }// 打印数组的地址信息#define INFO(a) \        { \         P(a) \         OUT(a) \        }int main(int argc, char *argv[]){    printf("-----二维数组-----\n");    printf("a[%d][%d]\n",ROWS,COLUMNS);    // #1 已知第二维    // 数组指针    char (*a1)[COLUMNS];    a1 = (char(*)[COLUMNS])calloc(ROWS,sizeof(char*));    printf("*****数组指针*****\n");    INFO(a1)    // #2 已知第一维    // 指针数组    char *a2[ROWS];    for(int i = 0; i < ROWS; i++) {        a2[i] = (char*)calloc(COLUMNS, sizeof(char));    }    printf("*****指针数组*****\n");    INFO(a2)    // #3 已知第一维，一次分配内存（保证内存分配的连续性）    // 指针数组    char *a3[ROWS];    a3[0] = (char *)calloc(ROWS*COLUMNS, sizeof(char));    for(int i = 1; i < ROWS; i++) {        a3[i] = a3[i-1] + COLUMNS;    }    printf("*****指针数组，一次分配内存*****\n");    INFO(a3)    // #4 两维都未知    // 二级指针    char **a4;    a4 = (char **)calloc(ROWS, sizeof(char*));    for(int i = 0; i < ROWS; i++) {        a4[i] = (char*)calloc(COLUMNS, sizeof(char));    }    printf("*****两维都未知*****\n");    INFO(a4)    // #5 两维都未知，一次分配内存（保证内存分配的连续性）    // 二级指针    char **a5;    a5 = (char**)calloc(ROWS, sizeof(char*));    a5[0] = (char*)calloc(ROWS*COLUMNS, sizeof(char));    for(int i = 1; i < ROWS; i++) {        a5[i] = a5[i-1] + COLUMNS;    }    printf("*****两维都未知，一次分配内存*****\n");    INFO(a5)    // 统一释放申请的内存空间    // free a1    free(a1);    // free a2    for(int i = 0; i < ROWS; i++) {        free(a2[i]);    }    // free a3    free(a3[0]);    // free a4    for(int i = 0; i < ROWS; i++) {        free(a4[i]);    }    free(a4);    // free a5    free(a5[0]);    free(a5);    return 0;}

输出结果

-----二维数组-----a[6][5]*****数组指针*****sizeof(a1): 4sizeof(a1[0]):  5a1:       addr:0x9bb2008a1[0]:    addr:0x9bb2008a1[1]:    addr:0x9bb200da1[2]:    addr:0x9bb2012a1[3]:    addr:0x9bb2017a1[4]:    addr:0x9bb201ca1[5]:    addr:0x9bb2021a1[0][0]: addr:0x9bb2008    a1[0][1]: addr:0x9bb2009    a1[0][2]: addr:0x9bb200a    a1[0][3]: addr:0x9bb200b    a1[0][4]: addr:0x9bb200c    a1[1][0]: addr:0x9bb200d    a1[1][1]: addr:0x9bb200e    a1[1][2]: addr:0x9bb200f    a1[1][3]: addr:0x9bb2010    a1[1][4]: addr:0x9bb2011    a1[2][0]: addr:0x9bb2012    a1[2][1]: addr:0x9bb2013    a1[2][2]: addr:0x9bb2014    a1[2][3]: addr:0x9bb2015    a1[2][4]: addr:0x9bb2016    a1[3][0]: addr:0x9bb2017    a1[3][1]: addr:0x9bb2018    a1[3][2]: addr:0x9bb2019    a1[3][3]: addr:0x9bb201a    a1[3][4]: addr:0x9bb201b    a1[4][0]: addr:0x9bb201c    a1[4][1]: addr:0x9bb201d    a1[4][2]: addr:0x9bb201e    a1[4][3]: addr:0x9bb201f    a1[4][4]: addr:0x9bb2020    a1[5][0]: addr:0x9bb2021    a1[5][1]: addr:0x9bb2022    a1[5][2]: addr:0x9bb2023    a1[5][3]: addr:0x9bb2024    a1[5][4]: addr:0x9bb2025    *****指针数组*****sizeof(a2): 24sizeof(a2[0]):  4a2:       addr:0xbfbbbc60a2[0]:    addr:0x9bb2028a2[1]:    addr:0x9bb2038a2[2]:    addr:0x9bb2048a2[3]:    addr:0x9bb2058a2[4]:    addr:0x9bb2068a2[5]:    addr:0x9bb2078a2[0][0]: addr:0x9bb2028    a2[0][1]: addr:0x9bb2029    a2[0][2]: addr:0x9bb202a    a2[0][3]: addr:0x9bb202b    a2[0][4]: addr:0x9bb202c    a2[1][0]: addr:0x9bb2038    a2[1][1]: addr:0x9bb2039    a2[1][2]: addr:0x9bb203a    a2[1][3]: addr:0x9bb203b    a2[1][4]: addr:0x9bb203c    a2[2][0]: addr:0x9bb2048    a2[2][1]: addr:0x9bb2049    a2[2][2]: addr:0x9bb204a    a2[2][3]: addr:0x9bb204b    a2[2][4]: addr:0x9bb204c    a2[3][0]: addr:0x9bb2058    a2[3][1]: addr:0x9bb2059    a2[3][2]: addr:0x9bb205a    a2[3][3]: addr:0x9bb205b    a2[3][4]: addr:0x9bb205c    a2[4][0]: addr:0x9bb2068    a2[4][1]: addr:0x9bb2069    a2[4][2]: addr:0x9bb206a    a2[4][3]: addr:0x9bb206b    a2[4][4]: addr:0x9bb206c    a2[5][0]: addr:0x9bb2078    a2[5][1]: addr:0x9bb2079    a2[5][2]: addr:0x9bb207a    a2[5][3]: addr:0x9bb207b    a2[5][4]: addr:0x9bb207c    *****指针数组，一次分配内存*****sizeof(a3): 24sizeof(a3[0]):  4a3:       addr:0xbfbbbc78a3[0]:    addr:0x9bb2088a3[1]:    addr:0x9bb208da3[2]:    addr:0x9bb2092a3[3]:    addr:0x9bb2097a3[4]:    addr:0x9bb209ca3[5]:    addr:0x9bb20a1a3[0][0]: addr:0x9bb2088    a3[0][1]: addr:0x9bb2089    a3[0][2]: addr:0x9bb208a    a3[0][3]: addr:0x9bb208b    a3[0][4]: addr:0x9bb208c    a3[1][0]: addr:0x9bb208d    a3[1][1]: addr:0x9bb208e    a3[1][2]: addr:0x9bb208f    a3[1][3]: addr:0x9bb2090    a3[1][4]: addr:0x9bb2091    a3[2][0]: addr:0x9bb2092    a3[2][1]: addr:0x9bb2093    a3[2][2]: addr:0x9bb2094    a3[2][3]: addr:0x9bb2095    a3[2][4]: addr:0x9bb2096    a3[3][0]: addr:0x9bb2097    a3[3][1]: addr:0x9bb2098    a3[3][2]: addr:0x9bb2099    a3[3][3]: addr:0x9bb209a    a3[3][4]: addr:0x9bb209b    a3[4][0]: addr:0x9bb209c    a3[4][1]: addr:0x9bb209d    a3[4][2]: addr:0x9bb209e    a3[4][3]: addr:0x9bb209f    a3[4][4]: addr:0x9bb20a0    a3[5][0]: addr:0x9bb20a1    a3[5][1]: addr:0x9bb20a2    a3[5][2]: addr:0x9bb20a3    a3[5][3]: addr:0x9bb20a4    a3[5][4]: addr:0x9bb20a5    *****两维都未知*****sizeof(a4): 4sizeof(a4[0]):  4a4:       addr:0x9bb20b0a4[0]:    addr:0x9bb20d0a4[1]:    addr:0x9bb20e0a4[2]:    addr:0x9bb20f0a4[3]:    addr:0x9bb2100a4[4]:    addr:0x9bb2110a4[5]:    addr:0x9bb2120a4[0][0]: addr:0x9bb20d0    a4[0][1]: addr:0x9bb20d1    a4[0][2]: addr:0x9bb20d2    a4[0][3]: addr:0x9bb20d3    a4[0][4]: addr:0x9bb20d4    a4[1][0]: addr:0x9bb20e0    a4[1][1]: addr:0x9bb20e1    a4[1][2]: addr:0x9bb20e2    a4[1][3]: addr:0x9bb20e3    a4[1][4]: addr:0x9bb20e4    a4[2][0]: addr:0x9bb20f0    a4[2][1]: addr:0x9bb20f1    a4[2][2]: addr:0x9bb20f2    a4[2][3]: addr:0x9bb20f3    a4[2][4]: addr:0x9bb20f4    a4[3][0]: addr:0x9bb2100    a4[3][1]: addr:0x9bb2101    a4[3][2]: addr:0x9bb2102    a4[3][3]: addr:0x9bb2103    a4[3][4]: addr:0x9bb2104    a4[4][0]: addr:0x9bb2110    a4[4][1]: addr:0x9bb2111    a4[4][2]: addr:0x9bb2112    a4[4][3]: addr:0x9bb2113    a4[4][4]: addr:0x9bb2114    a4[5][0]: addr:0x9bb2120    a4[5][1]: addr:0x9bb2121    a4[5][2]: addr:0x9bb2122    a4[5][3]: addr:0x9bb2123    a4[5][4]: addr:0x9bb2124    *****两维都未知，一次分配内存*****sizeof(a5): 4sizeof(a5[0]):  4a5:       addr:0x9bb2130a5[0]:    addr:0x9bb2150a5[1]:    addr:0x9bb2155a5[2]:    addr:0x9bb215aa5[3]:    addr:0x9bb215fa5[4]:    addr:0x9bb2164a5[5]:    addr:0x9bb2169a5[0][0]: addr:0x9bb2150    a5[0][1]: addr:0x9bb2151    a5[0][2]: addr:0x9bb2152    a5[0][3]: addr:0x9bb2153    a5[0][4]: addr:0x9bb2154    a5[1][0]: addr:0x9bb2155    a5[1][1]: addr:0x9bb2156    a5[1][2]: addr:0x9bb2157    a5[1][3]: addr:0x9bb2158    a5[1][4]: addr:0x9bb2159    a5[2][0]: addr:0x9bb215a    a5[2][1]: addr:0x9bb215b    a5[2][2]: addr:0x9bb215c    a5[2][3]: addr:0x9bb215d    a5[2][4]: addr:0x9bb215e    a5[3][0]: addr:0x9bb215f    a5[3][1]: addr:0x9bb2160    a5[3][2]: addr:0x9bb2161    a5[3][3]: addr:0x9bb2162    a5[3][4]: addr:0x9bb2163    a5[4][0]: addr:0x9bb2164    a5[4][1]: addr:0x9bb2165    a5[4][2]: addr:0x9bb2166    a5[4][3]: addr:0x9bb2167    a5[4][4]: addr:0x9bb2168    a5[5][0]: addr:0x9bb2169    a5[5][1]: addr:0x9bb216a    a5[5][2]: addr:0x9bb216b    a5[5][3]: addr:0x9bb216c    a5[5][4]: addr:0x9bb216d

参考

二维数组的动态分配及参数传递

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