1041 Be Unique (20 point(s)) - C语言 PAT 甲级

1041 Be Unique (20 point(s))

Being unique is so important to people on Mars that even their lottery is designed in a unique way. The rule of winning is simple: one bets on a number chosen from [1,10⁴]. The first one who bets on a unique number wins. For example, if there are 7 people betting on { 5 31 5 88 67 88 17 }, then the second one who bets on 31 wins.

Input Specification:

Each input file contains one test case. Each case contains a line which begins with a positive integer N (≤ 10⁵) and then followed by N bets. The numbers are separated by a space.

Output Specification:

For each test case, print the winning number in a line. If there is no winner, print None instead.

Sample Input:

7 5 31 5 88 67 88 17

Sample Output:

31

题目大意：

输入 N 个数字，按顺序读入，寻找第一个仅出现一次的数字，输出；若没有，则输出 None

设计思路：

两个数组，一个按顺序储存数字，另一个利用索引值储存对应数字的出现次数，再按顺序遍历一遍查找第一个仅出现一次的数字

编译器：C (gcc)

#include <stdio.h> int main(void) { int num[100001] = {0}, c[100001] = {0}; int n; int i; scanf("%d", &n); for (i = 0; i < n; i++) { scanf("%d", &num[i]); c[num[i]]++; } for (i = 0; i < n; i++) { if (c[num[i]] == 1) { printf("%d", num[i]); return 0; } } if (i >= n) { printf("None"); } return 0; }