C语言编程学习课件 (19).pdf

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1、Programming In CProgramming In C Nested if statement When a selection structure contains another selection structure,it is called a nested selection structure.the pairing relationship between if and else if(c1)if(c2)statement 1 else statement 2 else if(c3)statement 3 else statement 4 The C programmi

2、ng language stipulates that else is always paired with the nearest and unpaired if above it.Programming In CProgramming In C exercise：what value of x after code run？intint a=a=1 1,b=,b=3 3,c=,c=5 5,d=,d=4 4;ifif(ab)(ab)ifif(cd)(cd)x=x=1 1;elseelse ifif(ac)(ac)ifif(bd)(b=0)else printf(方程无实根！n);if (b*

3、b-4*a*c)0)x1=(-b+sqrt(b*b-4*a*c)/(2*a);x2=(-b-sqrt(b*b-4*a*c)/(2*a);printf(两个不等的实根：x1=%.2f x2=%.2fn,x1,x2);else x1=-b/(2*a);printf(两个相等的实根，x1=x2=%.2fn,x1);Programming In CProgramming In C void main()float a,b,c,x1,x2,delta;scanf(%f%f%f,&a,&b,&c);delta =b*b-4*a*c;/好风格 if (delta=0)if (delta0)x1=(-b+sq

4、rt(delta)/(2*a);x2=(-b-sqrt(delta)/(2*a);printf(两个不等的实根：x1=%.2f x2=%.2fn,x1,x2);else x1=-b/(2*a);printf(两个相等的实根，x1=x2=%.2fn,x1);else printf(方程无实根！n);Improved code Programming In CProgramming In C efficiency Improved code Prevent mistakes Improve readability Improve maintainability Programming In CProgramming In C