68 lines
1.2 KiB
C
68 lines
1.2 KiB
C
#include<stdio.h>
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#include<stdlib.h>
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//學長教我用雙重指標寫的
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void mul(int **a ,int **b,int **c ,int m , int k ,int n){
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int i , j , l ,sum;
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for (i=0;i<m;i++){
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for(j=0;j<n;j++){
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sum = 0;
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for(l=0;l<k;l++){
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sum += a[i][l]*b[l][j];
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}c[i][j]=sum;
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}
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}
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}
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int main(){
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int i , j ,m=2,k=3,n=4;
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//先定義兩個矩陣
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int a[2][3]={{1,2,7},{3,4,1}};
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int b[3][4]={{5,6,2,4},{7,8,2,4},{7,2,6,1}};
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//根據m,k,n配置記憶體空間
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int **arr_a = (int**)malloc(m * sizeof(int*));
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int **arr_b = (int**)malloc(k * sizeof(int*));
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int **arr_c = (int**)malloc(m * sizeof(int*));
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for(i=0;i<m;i++){
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arr_a[i] = (int*)malloc(k*sizeof(int));
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arr_c[i] = (int*)malloc(n*sizeof(int));
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}
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for(i=0;i<k;i++){
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arr_b[i] = (int*)malloc(n*sizeof(int));
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}
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//把值讀進 arr_a和arr_b
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for (i=0;i<m;i++){
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for(j=0;j<k;j++){
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arr_a[i][j]=a[i][j];
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}
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}
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for (i=0;i<k;i++){
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for(j=0;j<n;j++){
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arr_b[i][j]=b[i][j];
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}
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}
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mul(arr_a,arr_b,arr_c,m,k,n);
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for (i=0;i<m;i++){
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for(j=0;j<n;j++){
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printf("c[%d][%d]=%d\n",i,j,arr_c[i][j]);
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}
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}
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//根據矩陣大小釋放記憶體空間
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free (arr_a);
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free (arr_b);
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free (arr_c);
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for(i=0;i<m;i++){
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free (arr_a[i]);
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free (arr_c[i]);
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}
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for(i=0;i<k;i++){
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free (arr_b[i]);
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}
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return 0 ;
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}
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