杭电hdu 1455 sticks 深度优先搜索

http://acm.hdu.edu.cn/showproblem.php?pid=1455

```//深度优先搜索
#include <iostream>

using namespace std;

#include <algorithm>
#include <cstdio>
#include <cstring>

int sticks[65];
bool used[65], flag;

int n, len, piece;

bool cmp(int a, int b)
{
return a > b;
}

void dfs(int pos, int cur, int cnt)
{
if(flag)return ;//已搜索到当前解就返回
if(cur == len){
cnt ++;
if(cnt == piece){//当前解可行
flag = true;
}
dfs(0,0,cnt);
return ;
}
if(pos == n)return ;//搜到了最后一根stick
int pre = -1;
for(int i = pos; i < n; i ++){//从pos的位置继续搜索
if(!used[i] && sticks[i] != pre && cur + sticks[i] <= len){
pre = sticks[i];
used[i] = true;
dfs(i + 1, sticks[i] + cur, cnt);
used[i] = false;
if(flag||pos==0)return;
}
}
}

int main()
{
//	freopen("input.txt", "r+", stdin);
int i;
int sum, max;
while(scanf("%d", &n)&&n){
sum = 0;
for(i = 0; i < n; i ++){
scanf("%d", &sticks[i]);
sum += sticks[i];
}
sort(sticks, sticks+n, cmp);//降序排序
max = sticks[0];
for(i = max; i <= sum; i ++){//i为当前搜索的每根sitck的长度
if(sum%i==0){
piece = sum/i;//stick 的数目
len = i;
memset(used, false, sizeof(used));
flag = false;
dfs(0,0,0);
if(flag)break;
}
}
printf("%d\n", len);
}
return 0;
}```

```#include <iostream>

using namespace std;

#include <cstdio>
#include <cstring>
#include <algorithm>

int cmp(const void *a, const void *b)
{
return (*(int *)b)-(*(int *)a);
}

bool used[65];
int sticks[65];
int n, len, piece;

bool dfs(int pos, int cur, int cnt)
{
bool flag = (cur==0 ? true : false);
if(cnt == piece){
return true;
}
for(int i = pos; i < n; i ++){
if(used[i])continue;
if(cur + sticks[i] == len){
used[i] = true;
if(dfs(0,0,cnt+1))return true;
used[i] = false;
return false;
}
else if(cur + sticks[i] < len){
used[i] = true;
if(dfs(i+1, cur+sticks[i], cnt))
return true;
used[i] = false;
if(flag)return false;
while(sticks[i] == sticks[i+1])i++;
}
}
return false;
}

int main()
{
//	freopen("input.txt", "r", stdin);
//	freopen("output.txt", "w", stdout);
int sum, i;
while(scanf("%d", &n)&&n){
sum = 0;
for(i = 0; i < n; i ++){
scanf("%d", &sticks[i]);
sum += sticks[i];
}
qsort(sticks, n, sizeof(sticks[0]), cmp);
//		printf("%d\n", sticks[n-1]);
memset(used, false, sizeof(used));
for(len = sticks[0]; len <= sum; len ++){
if(sum%len==0){
piece = sum/len;
if(dfs(0,0,0)){
printf("%d\n", len);
break;
}
}
}
}
return 0;
}```