uvalive3667 ruler

tips:

回溯

use a queue to restore the temporary marked array(vis) , and when it back, set vis = 0

first floor give out all the received res, and combine with all the d to make new res, and mark all length which can get then,

code:

<pre name="code" class="cpp">#include<cstdio>#include<cmath>#include<string>#include<iostream>#include<algorithm>#include<cstring>#include<queue>using namespace std;const int maxn = 55;int d[maxn], vis[maxn];int pos[1000005];int n, len;int res[maxn];bool dfs(int cnt) {if(cnt == len) {for(int i=1; i<n; i++) {if(!vis[i]) return false;}return true;}queue<int> q;for(int i=1; i<cnt; i++)  {for(int j=1; j<n; j++) {if(!vis[j]) {int temp = res[i]+d[j];if(temp <= res[cnt-1] || temp >= d[n])continue;//make sure that the new answer is biger than everres[cnt] = temp;for(int k=1; k<cnt; k++) {temp = res[cnt]-res[k];if(vis[pos[temp]]==0 && pos[temp]) {q.push(pos[temp]);vis[pos[temp]] = 1;}}temp = d[n]-res[cnt];if(!vis[pos[temp]] && pos[temp]) {vis[pos[temp]] = 1;q.push(pos[temp]);}if(dfs(cnt+1)) return true;while(!q.empty()) {vis[q.front()]=0;q.pop();}}}}return false;}int main() {int kase=1;while(scanf("%d", &n) != EOF && n) {memset(vis, 0 ,sizeof(vis));memset(pos, 0, sizeof(pos));for(int i=1; i<=n; i++)scanf("%d", &d[i]);        sort(d + 1, d + 1 + n);          n = unique(d + 1, d + 1 + n) - d - 1;          for (int i = 1; i <= n; i++)              pos[d[i]] = i;          len = sqrt(2 * n) - 1;          res[1] = 0;          while (!dfs(2))              len++;          res[len] = d[n];          printf("Case %d:\n", kase++);          printf("%d\n", len);          for (int i = 1; i <= len; i++)              printf("%d ", res[i]);          printf("\n"); }return 0;}