测评
题目
leetcode 17
给定一个仅包含数字 2-9 的字符串,返回所有它能表示的字母组合。
给出数字到字母的映射如下(与电话按键相同)。注意 1 不对应任何字母。
示例:
输入:“23”
输出:[“ad”, “ae”, “af”, “bd”, “be”, “bf”, “cd”, “ce”, “cf”].
说明:
尽管上面的答案是按字典序排列的,但是你可以任意选择答案输出的顺序。
void dfs(char *digits, char *str, int ind, char letter[][5], char **res, int *returnSize) {
if (digits[ind] == '\0') {
str[ind] = '\0';
strcpy(res[*returnSize], str);
(*returnSize)++;//谨记*的符号低于++,记得加括号
return ;
}
int d = digits[ind] - '0', i = 0;
while (letter[d][i] != '\0') {
str[ind] = letter[d][i];
dfs(digits, str, ind + 1, letter, res, returnSize);
i++;
}
}
char ** letterCombinations(char * digits, int* returnSize){
*returnSize = 0;
if (digits[0] == '\0') return digits;
char letter[][5] = {"", "", "abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
int len = strlen(digits);
int count = 1;
for (int i = 0; i < len; i++) {
count *= 4;
}
char **res = (char **)malloc(sizeof(char *) * count);
for (int i = 0; i < count; i++) {
res[i] = (char *)malloc(sizeof(char) * (len + 1));
res[i][len] = '\0';
}
char *str = (char *)malloc(sizeof(char) * (len + 1));
dfs(digits, str, 0, letter, res, returnSize);
return res;
}