Algorithm 我可以将数组划分为K个大小吗?
我试图实现这个问题中的算法,但我缺少一些边缘情况,这导致我的代码进入无限循环。我可以通过做一些表面上的改变来修复它,但这表明我不理解算法 有人能帮我吗,我错过了什么Algorithm 我可以将数组划分为K个大小吗?,algorithm,dynamic-programming,partitioning,greedy,Algorithm,Dynamic Programming,Partitioning,Greedy,我试图实现这个问题中的算法,但我缺少一些边缘情况,这导致我的代码进入无限循环。我可以通过做一些表面上的改变来修复它,但这表明我不理解算法 有人能帮我吗,我错过了什么 #include <stdio.h> #define max(a, b) (((a)>(b))?(a):(b)); int get_max(int *a, int i, int size) { if (i >= size) return 0; return max(a[i],
#include <stdio.h>
#define max(a, b) (((a)>(b))?(a):(b));
int get_max(int *a, int i, int size)
{
if (i >= size)
return 0;
return max(a[i], get_max(a, i+1, size));
}
int get_sum(int *a, int i, int size)
{
if (i >= size)
return 0;
return a[i] + get_sum(a, i+1, size);
}
int get_partition(int *a, int size, int bound) {
int running_sum = 0;
int partitions = 0, i;
for (i=0;i<size;i++) {
if (a[i] + running_sum <= bound) {
running_sum += a[i];
} else {
running_sum = 0;
running_sum += a[i];
partitions++;
}
}
return partitions;
}
int foo(int *a, int size, int k)
{
int lower = get_max(a, 0, size);
int higher = get_sum(a, 0, size);
int partition;
while (lower < higher) {
int bound = (lower + (higher))/2;
partition = get_partition(a, size, bound);
printf("partition %d bound %d lower %d higher %d\n", partition, bound, lower, higher);
if (partition >= k)
lower = bound;
else
higher = bound;
}
return partition;
}
#define SIZE(a) sizeof(a)/sizeof(a[0])
int main(void) {
int a[] = {2, 3, 4, 5, 6};
printf("%d\n", foo(a, SIZE(a), 3));
return 0;
}
您有两个错误:
- 在二进制搜索过程中,您的while测试应该是
,而不是while(lower+1
。当while(lower
,lower=8
时,您将进入无限循环。在此阶段,您的higher=9
边界将是
(lower+higher)/2=8,您将更新
,这不会改变任何内容lower=bound
- 在
的末尾,您应该返回foo
(而不是partitions),因为您的二进制搜索不变量是具有higher
的不变量,您可以将其划分为bound=higher
或更少k
- 您对
的计算是错误的。您没有考虑最后一个分区组的帐户,因为您只有在溢出get\u partition
时才更新运行\u sum
分区
if (running_sum > 0) partitions++;
#include <stdio.h>
#define max(a, b) (((a)>(b))?(a):(b));
int get_max(int *a, int i, int size)
{
if (i >= size)
return 0;
return max(a[i], get_max(a, i+1, size));
}
int get_sum(int *a, int i, int size)
{
if (i >= size)
return 0;
return a[i] + get_sum(a, i+1, size);
}
int get_partition(int *a, int size, int bound) {
int running_sum = 0;
int partitions = 0, i;
for (i=0;i<size;i++) {
if (a[i] + running_sum <= bound) {
running_sum += a[i];
} else {
running_sum = 0;
running_sum += a[i];
partitions++;
}
}
if (running_sum > 0)
partitions++;
return partitions;
}
int foo(int *a, int size, int k)
{
int lower = get_max(a, 0, size);
int higher = get_sum(a, 0, size);
int partition;
while (lower+1 < higher) {
int bound = (lower + (higher))/2;
partition = get_partition(a, size, bound);
printf("partition %d bound %d lower %d higher %d\n", partition, bound, lower, higher);
if (partition > k)
lower = bound;
else
higher = bound;
}
printf("partition %dlower %d higher %d\n", partition, lower, higher);
return higher;
}
#define SIZE(a) sizeof(a)/sizeof(a[0])
int main(void) {
int a[] = {2, 3, 4, 5, 6};
printf("%d\n", foo(a, SIZE(a), 3));
return 0;
}
#包括
#定义max(a,b)((a)>(b))?(a):(b));
int get_max(int*a,int i,int size)
{
如果(i>=大小)
返回0;
returnmax(a[i],get_max(a,i+1,size));
}
int get_sum(int*a,int i,int size)
{
如果(i>=大小)
返回0;
返回一个[i]+get_和(a,i+1,size);
}
int-get_分区(int*a,int-size,int-bound){
int运行_sum=0;
int分区=0,i;
对于(i=0;i k)
下限=下限;
其他的
更高=界限;
}
printf(“分区%d低%d高%d\n”,分区,低,高);
回报更高;
}
#定义大小(a)sizeof(a)/sizeof(a[0])
内部主(空){
inta[]={2,3,4,5,6};
printf(“%d\n”,foo(a,大小(a),3));
返回0;
}
请包括输出的前两行和前三行。猜测:lower==bound==higher-1#include <stdio.h>
#define max(a, b) (((a)>(b))?(a):(b));
int get_max(int *a, int i, int size)
{
if (i >= size)
return 0;
return max(a[i], get_max(a, i+1, size));
}
int get_sum(int *a, int i, int size)
{
if (i >= size)
return 0;
return a[i] + get_sum(a, i+1, size);
}
int get_partition(int *a, int size, int bound) {
int running_sum = 0;
int partitions = 0, i;
for (i=0;i<size;i++) {
if (a[i] + running_sum <= bound) {
running_sum += a[i];
} else {
running_sum = 0;
running_sum += a[i];
partitions++;
}
}
if (running_sum > 0)
partitions++;
return partitions;
}
int foo(int *a, int size, int k)
{
int lower = get_max(a, 0, size);
int higher = get_sum(a, 0, size);
int partition;
while (lower+1 < higher) {
int bound = (lower + (higher))/2;
partition = get_partition(a, size, bound);
printf("partition %d bound %d lower %d higher %d\n", partition, bound, lower, higher);
if (partition > k)
lower = bound;
else
higher = bound;
}
printf("partition %dlower %d higher %d\n", partition, lower, higher);
return higher;
}
#define SIZE(a) sizeof(a)/sizeof(a[0])
int main(void) {
int a[] = {2, 3, 4, 5, 6};
printf("%d\n", foo(a, SIZE(a), 3));
return 0;
}