C++如何判断运算结果溢出

时间：2021-10-27 02:14:24
对于有符号整数的溢出，只需要简单判断运算结果符号是否与操作数相等即可；下面我们讨论无符号integer的溢出检测问题： 假设我们有两个变量a和b，size 为n，最大值为R。'+'代表实际的数学运算符--加号，‘$’代表计算机中的运算。 加法溢出 显然如果a+b<=R-1;a$b=a+b; 如果a+b>=R;a$b=a+b-R; 分析：由于R比a和b都大，所以a-R与b-R都是负值，所以我们有a+b-R<a;a+b-R<b; 乘法溢出 1.如果a*b>max，则有a>max/b;(如果无符号，max=R-1;否则max=R/2-1) 
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int is_mul_overflow(int a, int b) {    if( a >= 0 && b >=0  ) {        return INT_MAX / a < b;    }    else if( a < 0 && b < 0 ) {        return INT_MAX / a > b;    }    else if( a * b == INT_MIN ) {        return 0;    }    else {        return a < 0 ? is_mul_overflow(-a, b) : is_mul_overflow(a, -b);    }}
 来自CODE的代码片JudgeOveFlow.cpp

参考：http://www.cplusplus.com/articles/DE18T05o/
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