题目：

题解：

struct Trie {int ch[26];bool flag;
} trie[10001];int size;void insert(char* s, int sSize) {int add = 0;for (int i = 0; i < sSize; i++) {int x = s[i] - 'a';if (trie[add].ch[x] == 0) {trie[add].ch[x] = ++size;memset(trie[size].ch, 0, sizeof(trie[size].ch));trie[size].flag = false;}add = trie[add].ch[x];}trie[add].flag = true;
}bool find(char* s, int sSize) {int add = 0;for (int i = 0; i < sSize; i++) {int x = s[i] - 'a';if (trie[add].ch[x] == 0) {return false;}add = trie[add].ch[x];}return trie[add].flag;
}char** ans[1001];
int ansSize[1001];void backtrack(char* s, int sSize, int index) {if (ans[index] == NULL) {ans[index] = malloc(sizeof(char**));if (index == sSize) {ansSize[index] = 1;char* tmp = malloc(sizeof(char));tmp[0] = '\0';ans[index][0] = tmp;return;}ansSize[index] = 0;for (int i = index + 1; i <= sSize; ++i) {int len = i - index;char* word = malloc(sizeof(char) * (len + 1));for (int j = 0; j < len; ++j) word[j] = s[index + j];word[len] = '\0';if (find(word, len)) {backtrack(s, sSize, i);ans[index] = realloc(ans[index], sizeof(char**) * (ansSize[index] + ansSize[i]));for (int j = 0; j < ansSize[i]; ++j) {int len1 = len, len2 = strlen(ans[i][j]);char* tmp = malloc(sizeof(char) * (len1 + len2 + 2));strcpy(tmp, word);if (len2 > 0) {tmp[len1] = ' ';}strcpy(tmp + len1 + 1, ans[i][j]);ans[index][ansSize[index]++] = tmp;}}}}
}char** wordBreak(char* s, char** wordDict, int wordDictSize, int* returnSize) {memset(ans, 0, sizeof(ans));size = 0;memset(trie[0].ch, 0, sizeof(trie[0].ch));trie[0].flag = false;for (int i = 0; i < wordDictSize; i++) {insert(wordDict[i], strlen(wordDict[i]));}backtrack(s, strlen(s), 0);*returnSize = ansSize[0];return ans[0];
}