127 lines
2.6 KiB
C
127 lines
2.6 KiB
C
#include <stdio.h>
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/**
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* https://leetcode-cn.com/problems/divide-two-integers/description/
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* 两数相除,不能直接使用乘法除法
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*/
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int add(int num1, int num2)
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{
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while (num2)
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{
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int tmp = num1 ^ num2;
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num2 = (num1 & num2) << 1;
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num1 = tmp;
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}
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return num1;
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}
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int sub(int num1, int num2)
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{
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return add(num1, add(~num2, 1));
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}
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int negative(int num) //判断负数
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{
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return (num >> 31) & 1;
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}
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int abs_(int num)
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{
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if (negative(num)) //右移31位判断正负
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{
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return add(~num, 1); //负数
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}
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return num;
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}
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int divide(int dividend, int divisor)
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{
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int flag = 1;
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if (negative(dividend) == negative(divisor))
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{
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flag = 0;
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}
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unsigned int x = abs_(dividend);
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unsigned int y = abs_(divisor);
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unsigned int result = 0;
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for (int i = 31; i >= 0; i--)
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{
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if ((x >> i) >= y)
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{
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result = add(result, 1 << i);
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x = sub(x, y << i);
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}
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}
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if (flag)
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{
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//负数
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if (result > 2147483648)
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{
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return 2147483647;
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}
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return add(~result,1);
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}
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else
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{
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//正数
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if (result > 2147483647)
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{
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return 2147483647;
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}
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return result;
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}
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}
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/*
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对于int a = 0x80000000;
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long long int b = -a;
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而言，b依然是-2147483648，只不过是长长整型的-2147483648
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可能是右边的-a运算，由于预期的结果溢出，所以就没有做负号运算
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原先认为的是-a会导致溢出从而结果为0，实际测试发现不是
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long long int d = ((long long int)dividend > 0) ? (long long int)dividend : -(long long int)dividend;
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long long int div = ((long long int)divisor > 0) ? (long long int)divisor : -(long long int)divisor;
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*/
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/**
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int divide(int dividend, int divisor) {
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if (divisor == 1)
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return dividend;
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if (divisor == -1)
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{
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if (dividend == (int)0x80000000)
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return 0x7FFFFFFF;
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else
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return -dividend;
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}
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int cnt = 0, factor = 0, i = 0;
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long long int d = dividend;
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long long int div = divisor;
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d = (d > 0) ? d : -d;
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div = (div > 0) ? div : -div;
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if ((dividend ^ divisor) & 0x80000000)
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factor = -1;
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else
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factor = 1;
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while (d >= div)
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{
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i = 0;
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while (d >= (div << i))
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{
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d -= (div << i);
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cnt += (1 << i++);
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}
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}
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return factor*cnt;
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}
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*/
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int main()
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{
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printf("%d\n", divide(-2147483648, -1));
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getchar();
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return 0;
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} |