Question

我正在尝试在http://www.programming-challenges.com提交我的代码，但我只得到错误的答案。我已经尝试了1000000这样的大输入数字来测试，我的代码返回了答案。如果有人可以提供帮助，我会非常感激。无论如何，这是我的代码：

#include <stdio.h>

unsigned int max_cycle(unsigned int i, unsigned int j);
unsigned int cycle_size(unsigned int m);
void swap(unsigned int *m, unsigned int *n);

int main(int argc, char *argv[]) {
   unsigned int a, b;
   int scan;

   scan = scanf("%u %u", &a, &b);
   printf("%u %u %u", a, b, max_cycle(a, b));
   while (scan> 0) {
       if((scan = scanf("%u %u", &a, &b)) > 0) {
           printf("\n%u %u %u", a, b, max_cycle(a, b));
       }
   }

   return 0;
}

unsigned int max_cycle(unsigned int x, unsigned int y) {
    unsigned int length = 0;
    unsigned int max = 0;

    if(x > y) {
        swap(&x, &y);
    }

    x++;
    while(x < y) {
        length = cycle_size(x);

        if(length > max) {
            max = length;
        }

        x++;
    }

    return max;
}

unsigned int cycle_size(unsigned int x) {
    unsigned int cntr = 1;

    while(x != 1) {
        if(x % 2 == 0) {
            x = x/2;
        } else {
            x = 3*x+1;
        }

        cntr++;
    }

    return cntr;    
}

void swap(unsigned int *x, unsigned int *y) {
    unsigned int term = 0;

    term = *x;
    *x = *y;
    *y = term;
}

Answer 1

您的代码中存在致命错误。你完全忽略了整数溢出。在找到x开始不符合32位的序列之前，您不必长时间搜索。由于具有不适合32位的序列的x很可能会创建一个长周期，因此您可能会错过具有最大周期长度的数字。

64位会更进一步，但不是那么多。

Answer 2

您的计划的输出缺少最终\n。取代

   int scan;

   scan = scanf("%u %u", &a, &b);
   printf("%u %u %u", a, b, max_cycle(a, b));
   while (scan> 0) {
       if((scan = scanf("%u %u", &a, &b)) > 0) {
           printf("\n%u %u %u", a, b, max_cycle(a, b));
       }
   }

与

    while (scanf("%u%u", &a, &b) == 2)
        printf("%u %u %u\n", a, b, max_cycle(a, b));

解决这个问题。

3n + 1猜想中的最大循环长度

2 个答案: