HDU-1671-Phone List
HDU-1671-Phone List
http://acm.hdu.edu.cn/showproblem.php?pid=1671
字典树，判断是否有某个数字是另一个数字的前缀，注意123不是123的前缀，建树之后要删除节点，否则会Memory LimitExceeded
写的比较麻烦，分两种情况，一是先出现123，再出现1234,；二是先出现1234，再出现123
#include<iostream>#include<cstdio>#include<cstring>#include<cstdlib>using namespace std;#define N 10005char str[N];struct node{ int count; node *childs[10]; node() { count=0; int i; for(i=0;i<=9;i++) childs[i]=NULL; }};node *root,*current,*newnode;int flag;void del(node *head) { int i; for(i=0;i<=9;i++) if(head->childs[i]!=NULL) del(head->childs[i]); delete(head);}int judge(node *head){ int i; for(i=0;i<=9;i++) if(head->childs[i]!=NULL) return 1; return 0;}void insert(char *str){ int i,m; current=root; for(i=0;i<strlen(str);i++) { m=str[i]-'0'; if(current->childs[m]!=NULL) { current=current->childs[m]; if((i<strlen(str)-1&¤t->count==1)||(i==strlen(str)-1&&judge(current))) { flag=1; break; } } else { newnode=new node; current->childs[m]=newnode; current=newnode; } } current->count=1;}int main(){ int t,i,n; scanf("%d",&t); while(t--) { scanf("%d",&n); flag=0; root=new node; while(n--) { scanf("%s",str); if(flag==1) continue; insert(str); } if(flag) printf("NO\n"); else printf("YES\n"); del(root); } return 0;}