hello-algo/codes/c/chapter_searching/leetcode_two_sum.c

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/**
* File: leetcode_two_sum.c
* Created Time: 2023-01-19
* Author: Reanon (793584285@qq.com)
*/
#include "../include/include.h"
/* 方法一:暴力枚举 */
int *twoSumBruteForce(int *nums, int numsSize, int target, int *returnSize) {
for (int i = 0; i < numsSize; ++i) {
for (int j = i + 1; j < numsSize; ++j) {
if (nums[i] + nums[j] == target) {
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int *res = malloc(sizeof(int) * 2);
res[0] = i, res[1] = j;
*returnSize = 2;
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return res;
}
}
}
*returnSize = 0;
return NULL;
}
/* 哈希表 */
struct hashTable {
int key;
int val;
UT_hash_handle hh; // 基于 uthash.h 实现
};
typedef struct hashTable hashTable;
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/* 哈希表查询 */
hashTable *find(hashTable *h, int key) {
hashTable *tmp;
HASH_FIND_INT(h, &key, tmp);
return tmp;
}
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/* 哈希表元素插入 */
void insert(hashTable *h, int key, int val) {
hashTable *t = find(h, key);
if (t == NULL) {
hashTable *tmp = malloc(sizeof(hashTable));
tmp->key = key, tmp->val = val;
HASH_ADD_INT(h, key, tmp);
} else {
t->val = val;
}
}
/* 方法二:辅助哈希表 */
int *twoSumHashTable(int *nums, int numsSize, int target, int *returnSize) {
hashTable *hashtable = NULL;
for (int i = 0; i < numsSize; i++) {
hashTable *t = find(hashtable, target - nums[i]);
if (t != NULL) {
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int *res = malloc(sizeof(int) * 2);
res[0] = t->val, res[1] = i;
*returnSize = 2;
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return res;
}
insert(hashtable, nums[i], i);
}
*returnSize = 0;
return NULL;
}
/* Driver Code */
int main() {
// ======= Test Case =======
int nums[] = {2, 7, 11, 15};
int target = 9;
// ====== Driver Code ======
int returnSize;
int *res = twoSumBruteForce(nums, sizeof(nums) / sizeof(int), target, &returnSize);
// 方法一
printf("方法一 res = ");
printArray(res, returnSize);
// 方法二
res = twoSumHashTable(nums, sizeof(nums) / sizeof(int), target, &returnSize);
printf("方法二 res = ");
printArray(res, returnSize);
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return 0;
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}