// http://h...content-available-to-author-only...h.net/test/read.cgi/tech/1320365280/544-545
#include <stdio.h>
#define LEN(array) ((sizeof array) / (sizeof array[0]))
 
int main(void)
{
    double vx[5];
    double *vxp;
    int i;
    printf("%dつの実数を入力してください\n", LEN(vx));
    for (i = 0, vxp = vx; i < LEN(vx); i++, vxp++) {
        printf("vx[%d] = ", i);
        scanf("%lf", vxp);
    }
    for (i = 0, vxp = vx; i < LEN(vx); i++, vxp++) {
        *vxp *= -1;
    }
    printf("正負を反転させました。 \n");
    for (i = 0, vxp = vx; i < LEN(vx); i++, vxp++) {
        printf("vx[%d] = %f\n", i, *vxp);
    }
    return 0;
}
 

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1.1
2.2
-3.3
4.4
-5.5