poj_2503 哈希

来源：互联网发布：mac怎么选中不同文字编辑：程序博客网时间：2024/06/14 22:15

题意：输入key value对的字典，要求再次输入value要能给出key，如果不存在输出'eh'

使用哈希方法，对字符串使用ELFHash函数，这题最重要的是对输入数据的处理。

code：

<span style="font-size:18px;">#include <iostream>using namespace std;const int HASH_BASE = 100001;int hashTable[HASH_BASE];int cur;char ans[11];struct HashNode{char s1[11];char s2[11];int next;};HashNode node[100005];void initHash(){for (int i = 0; i < HASH_BASE; i++){hashTable[i] = -1;}cur = 0;}int ELFhash(char *key){unsigned long h = 0;unsigned long x = 0;while (*key){h = (h << 4) + (*key++);  //h左移4位，当前字符ASCII存入h的低四位if ((x = h & 0xF0000000L) != 0){ //如果最高位不为0，则说明字符多余7个，如果不处理，再加第九个字符时，第一个字符会被移出//因此要有如下处理h ^= (x >> 24);//清空28~31位h &= ~x;}}return h % HASH_BASE;}void insertHash(char s1[],char s2[]){int value = ELFhash(s2);strcpy(node[cur].s1,s1);strcpy(node[cur].s2,s2);node[cur].next = hashTable[value];hashTable[value] = cur;cur++;}bool searchHash(char s[]){int value = ELFhash(s);int next = hashTable[value];while (next != -1){if (strcmp(s, node[next].s2) == 0){strcpy(ans,node[next].s1);return true;}next = node[next].next;}return false;}int main(){char s1[11],s2[11],t;initHash();while (true){char temp;if ((temp = getchar()) == '\n')break;s1[0] = temp;int i = 1;while (true){temp = getchar();if (temp == ' '){s1[i] = '\0';break;}elses1[i++] = temp;}cin >> s2;getchar();insertHash(s1,s2);}char word[11];while (cin >> word){memset(ans,'\0',sizeof(ans));if (searchHash(word))cout << ans << endl;elsecout << "eh" << endl;}//system("pause");return 0;}</span>

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