25 lines
555 B
C
25 lines
555 B
C
/*-------------------------------------------------------
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功能：输入一个圆半径（r），当r>＝0时，计算并输出圆的面积(area)和周长(circumference)，否则，输出提示信息。
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--------------------------------------------------------*/
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#include <stdio.h>
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#define PI 3.14
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main()
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{
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float r,s,l;
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printf("please input r:\n");
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scanf("%f",&r);
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if (r>=0)
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{
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/**********Program**********/
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s = PI * r*r;
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l = 2*PI*r;
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/********** End **********/
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printf("the area is %f\n",s);
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printf("the circumference is %f\n",l);
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}
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else
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printf("input error!\n");
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}
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