对称矩阵压缩和三种解压缩方式

#include
#include
#include
#define SIZE 5
using namespace std;

int* Compress(int *m) {
    int*n = (int*)malloc(sizeof(int)*(SIZE*(SIZE+1)/2));
    int i = 0;
    int j = 0;
    int k = 0;
    for (i = 0; i < SIZE; i++) {
        for (j = 0; j < SIZE; j++, k++) {
            if (i >= j)k = i*(i + 1) / 2 + j;
            else k = j*(j + 1) / 2 + i;
            n[k] = m[i*SIZE+j];
        }
    }
    return n;
}

int* Decompress1(int* n) {
    int * m = (int*)malloc(sizeof(int)*SIZE*SIZE);
    int i = 0;
    int j = 0;
    int k = 0;
    for (i = 0; i < SIZE; i++) {
        for (j = 0; j <= i; j++) {
            if (i >= j)k = i*(i + 1) / 2 + j ;
            else k = j*(j + 1) / 2 + i;
            m[j*SIZE+i] = m[i*SIZE+j] = n[k];
        }
    }
    return (int*)m;
}

int * Decompress2(int* n) {
    int * m = (int*)malloc(sizeof(int)*SIZE*SIZE);
    int i = 0;
    int j = 0;
    int k = 0;
    for (k = 0; k < (SIZE*(SIZE + 1) / 2); k++) {
        for (i = 0; (i + 1)*(i + 2) / 2 < k + 1; i++);
        j = k - i*(i + 1) / 2;
        m[j*SIZE+i] = m[i*SIZE + j] = n[k];
    }
    return m;
}

int * Decompress3(int * n) {
    int * m = (int*)malloc(sizeof(int)*SIZE*SIZE);
    int i = 0;
    int j = 0;
    int k = 0;
    for (k = 0; k < (SIZE)*(SIZE + 1) / 2; k++) {
        i =ceil( sqrt(2*k*1.0 + 2.25) - 1.5);
        j = k - i*(i + 1) / 2;
        m[j*SIZE + i] = m[i*SIZE + j] = n[k];
    }
    return m;
}

int main() {
    int p[SIZE][SIZE] = { 1,5,1,3,7,5,0,8,0,0,1,8,9,2,6,3,0,2,5,1,7,0,6,1,3};
    printf("压缩前：\n");
    for (int i = 0; i < SIZE; i++) {
        for (int j = 0; j < SIZE; j++)
            printf("%d ", p[i][j]);
        printf("\n");
    }
    int* p1 = Compress((int*)p);
    printf("压缩后：\n");
    for (int i = 0; i < (SIZE*(SIZE + 1) / 2); i++)printf("%d ", p1[i]);
    printf("\n");
    printf("解压前：\n");
    for (int i = 0; i < (SIZE*(SIZE + 1) / 2); i++)printf("%d ", p1[i]);
    printf("\n");
    printf("解压后：\n");
    int* p2 = Decompress1((int*)p1);
    for (int i = 0; i < SIZE; i++) {
        for (int j = 0; j < SIZE; j++)
            printf("%d ", p2[i*SIZE+j]);
        printf("\n");
    }
    printf("解压后：\n");
    p2 = Decompress2((int*)p1);
    for (int i = 0; i < SIZE; i++) {
        for (int j = 0; j < SIZE; j++)
            printf("%d ", p2[i*SIZE + j]);
        printf("\n");
    }
    printf("解压后：\n");
    p2 = Decompress3((int*)p1);
    for (int i = 0; i < SIZE; i++) {
        for (int j = 0; j < SIZE; j++)
            printf("%d ", p2[i*SIZE + j]);
        printf("\n");
    }
}