目录

题目

解法一：回溯

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题目

解法一：回溯

void swap(char* a, char* b) {char tmp = *a;*a = *b;*b = tmp;
}void reverse(char* str) {int start = 0, end = strlen(str) - 1;while (start < end) {swap(&str[start++], &str[end--]);}
}bool search(char** board, int m, int n, int i, int j,const char* word, int index) {if (word[index] == '\0') {return true;}if (i < 0 || i == m || j < 0 || j == n || word[index] != board[i][j]) {return false;}board[i][j] = '#';bool exist = search(board, m, n, i - 1, j, word, index + 1) || search(board, m, n, i + 1, j, word, index + 1) || search(board, m, n, i, j - 1, word, index + 1) || search(board, m, n, i, j + 1, word, index + 1);board[i][j] = word[index];return exist;
}bool exist(char** board, int boardSize, int* boardColSize, char* word) {const int m = boardSize, n = *boardColSize;int boardLetterCnts[128] = {0};for (int i = 0; i < m; i++) {for (int j = 0; j < n; j++) {boardLetterCnts[board[i][j]]++;}}int wordLetterCnts[128] = {0};int len = strlen(word);for (int i = 0; i < len; i++) {wordLetterCnts[word[i]]++;}for (int i = 'A'; i <= 'Z'; i++) {if (boardLetterCnts[i] < wordLetterCnts[i] || boardLetterCnts[i + 32] < wordLetterCnts[i + 32]) {return false;}}char newWord[len + 1];strcpy(newWord, word);if (wordLetterCnts[word[0]] > wordLetterCnts[word[len - 1]]) {reverse(newWord);}for (int i = 0; i < m; i++) {for (int j = 0; j < n; j++) {if (search(board, m, n, i, j, newWord, 0)) {return true;}}}return false;
}