Leetcode ☞ 217. Contains Duplicate

网址：https://leetcode.com/problems/contains-duplicate/

217. Contains Duplicate

My Submissions

Question

Total Accepted: 71959 Total
Submissions: 178180 Difficulty: Easy

Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct.

我的AC：

bool containsDuplicate(int* nums, int numsSize) {
int i, j;
for(i = 0; i < numsSize ; i ++){
for(j = i + 1 ; j <numsSize; j++){
if (nums[i] == nums[j])
return true;
}
}
return false;
}

缺点：1568ms。时间太长。如果先把nums数组排序再进行比较，就快的多了（仅需比较相邻的是否相同）。

改进：

int comp(const int *a, const int *b) {
if (*a > *b) return 1;
else if (*a < *b) return -1;
else return 0;
}

bool containsDuplicate(int* nums, int numsSize) {
if (numsSize < 2) {
return false;
}
qsort(nums, numsSize, sizeof(int), comp);
for (int i = 0; i < numsSize - 1; i++) {
if (nums[i] == nums[i+1]) {
return true;
}
}
return false;
}

其中comp函数也可以写成：
int comp (const void * a, const void * b) {
return ( *(int*)a - *(int*)b );
}