C语言每日一题

66. 加一

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */

 /*
 从后向前(从个位)开始+1,逢九进一,不为九时结束,全为九时数组长度加一
解法如下: 特别要注意的是returnSize,这个代表返回指针的长度,要不上层代码不知道要取多少个
*/
int* plusOne(int* digits, int digitsSize, int* returnSize)
{
    for (int i = digitsSize - 1; i >= 0; i--) {
        if (digits[i] == 9) {
            digits[i] = 0;
        } else {
            digits[i]++;
            *returnSize = digitsSize;
            return digits;
        }
    }

    int *res = malloc(sizeof(int) * (digitsSize + 1));
    memset(res, 0, sizeof(int) * (digitsSize + 1));
    *returnSize = digitsSize + 1;
    res[0] = 1;
    return res;
}

 

735. 行星碰撞

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
int* asteroidCollision(int* asteroids, int asteroidsSize, int* returnSize)
{
    *returnSize = 0;
    if (asteroids == NULL) {
        return NULL;
    }

    int *res = malloc(sizeof(int) * asteroidsSize);
    int idx = 0;
    for (int i = 0; i < asteroidsSize; i++) {
        res[idx++] = asteroids[i];
        // 碰撞条件：左正右负
        while (idx >= 2 && res[idx - 2] > 0 && res[idx - 1] < 0) {
            int left = res[idx - 2];
            int right = res[idx - 1];
            if (abs(left) == abs(right)) {
                idx -= 2;
            } else if (abs(left) < abs(right)) {
                res[idx - 2] = right;
                idx--;
            } else {
                idx--;
            }
        }
    }

    *returnSize = idx;
    return res;
}

 

3. 无重复字符的最长子串

typedef struct {
    int c; // 要用int
    int value;
    UT_hash_handle hh;
} hashTable;

hashTable *g_hash = NULL;

hashTable* FindNode(int ic)
{
    hashTable* tmp = NULL;
    HASH_FIND_INT(g_hash, &ic, tmp);
    return tmp;
}

void AddNode(int ic)
{
    hashTable *it = FindNode(ic);
    if (it == NULL) {
        it = malloc(sizeof(hashTable));
        it->c = ic;
        HASH_ADD_INT(g_hash, c, it);
    }
    it->value = 1;
}

void DelNode(int ic)
{
    hashTable *it = FindNode(ic);
    if (it != NULL) {
        HASH_DEL(g_hash, it);
        it->value = 0;
        free(it);
    }
}

void ClearAllNode()
{
    hashTable *curr, *tmp;
    HASH_ITER(hh, g_hash, curr, tmp) {
        HASH_DEL(g_hash, curr);
        free(curr);
    }
}

int lengthOfLongestSubstring(char * s)
{
    if (s == NULL) {
        return 0;
    }
    if (s[0] == '\0') {
        return 0;
    }

    int start = 0;
    int end = 0;
    int max = 0;
    int subLen = 0;
    while (s[end] != '\0') {
        if (FindNode((int)s[end]) == NULL) {
            AddNode((int)s[end]);
            subLen = end - start + 1;
            max = subLen > max ? subLen : max;
            end++;
        } else {
            DelNode((int)s[start]);
            start++;
        }
    }
    ClearAllNode();
    return max;
}