大整数相乘,C/C++ 判断两个整数相乘是否溢出

判断两int相乘是否溢出，目前找到的最正确方式： 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); } } void check(int n1, int n2, int expect_ret, int case_n) { int ret = is_mul_overflow(n1, n2); if( expect_ret == is_mul_overflow(n1, n2) ) printf("test pass case:%d\n",case_n); else printf("test fail case:%d\n",case_n); } int main() { int case_n = 0; check(1, 0x80000000, 0, ++case_n); check(-1, 0x80000000, 1, ++case_n); check(0x80000000, -1, 1, ++case_n); check(-1, 0x80000001, 0, ++case_n); check(0x80000001, -1, 0, ++case_n); check(1, 0x7fffffff, 0, ++case_n); check(0x7fffffff, 1, 0, ++case_n); check(2, 0x7fffffff, 1, ++case_n); check(0x7fffffff, 2, 1, ++case_n); check(0x7fffffff, -1, 0, ++case_n); check(-1, 0x7fffffff, 0, ++case_n); check(2, 0xc0000000, 0, ++case_n); check(0xc0000000, 2, 0, ++case_n); check(0x70000000, 2, 1, ++case_n); check(2, 0x70000000, 1, ++case_n); printf("%x\n", INT_MIN); printf("%x\n", INT_MAX); return 0; }
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