尝试用 C 编写单词搜索程序

Question

给定一个从文件中读入的用于所有测试用例的输入字典，以及几个单词搜索网格，我想从字典中识别出现在每个单词搜索网格中的所有单词。

我已阅读 dictionary.txt 文件，我相信它可以阅读任何字母网格，但我无法在网格中找到出现在 dictionary.txt 文件中的单词.我决定对所有方向的字符串使用递归二进制搜索，但这对我来说有点复杂。

我的程序一直运行到它到达单词搜索功能，它试图在网格中找到单词，但它会崩溃，但我不知道为什么，也不确定我是否在正确的轨道上。

这是我认为错误的部分，

int binsearch(char** dictionary, char** puzzle, int low, int high){

int mid;

if(low == 0 && high == 0){
    return 0;
}

mid = (low+high)/2 ;

if(strcmp(*puzzle,dictionary[mid]) == 0){
        //found a match
    return 1;
}

else if(strcmp(*puzzle,dictionary[mid]) > 0){
        //check upper half
    return binsearch(dictionary,puzzle,mid+1,high);
}

else if(strcmp(*puzzle,dictionary[mid]) < 0){
    //check lower half
    return binsearch(dictionary,puzzle,low,mid-1);
}
else return 0;

}

char wordSearch(char** dictionary, char** puzzle, int row, int col){

int i, X, Y, dir = 0;
char* wordsfound[20]= {'[=10=]'};
for (X=0;X<row+1;X++){
    for(Y=0;Y<col;Y++){
        for(dir=0;dir<DX_SIZE;dir++) //check every direction
            for(i=0;i<19;i++){
                //will continue in direction DX,DY starting at x,y
                int nextX = X + DX[dir] * i;
                int nextY = Y + DY[dir] * i;
                if(nextX < 0 || nextX >= row) break; //keep in bounds
                if(nextY < 0 || nextY >= col) break;
                //store the string of letters
                *wordsfound[i] = (puzzle[nextX][nextY]);
                if(i>2){ //minimum word is 3
                //if the string of letters is actually a word, print
                    int bin = binsearch(dictionary,wordsfound,1,listlength);
                    if(bin){
                        printf("%s\n",wordsfound);
                    }
                }
            }
    }
}

}

但这是我的全部代码

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define listlength 149256
#define maxWordLen 19


char** getWords(int rows, int cols);
void freeArray(char** array, int rows);
char** makeGridArray(int rows, int cols);
int binsearch(char** dictionary, char** puzzle, int low, int high);
char wordSearch(char** dictionary, char** puzzle, int row, int col);
const int DX_SIZE = 8;
const int DX[] = {-1,-1,-1,0,0,1,1,1};
const int DY[] = {-1,0,1,-1,1,-1,0,1};

int main(){

    //read in dictionary
    int i,j,x=0, numCases, gridRow, gridCol;
    char** words = getWords(listlength, maxWordLen);

    //Get number of cases.

    printf("enter number of cases:\n");
    scanf("%d", &numCases);

    //process each case.

    while(x < numCases){

        scanf("%d%d",&gridRow,&gridCol);

        //make word search grid
        char** grid = makeGridArray(gridRow+1, gridCol);

        /* for testing if grid is storing properly

        for(i=0; i<gridRow+1;i++){
            printf("%s\n",grid[i]);
        }

        */
        printf("Words Found Grid #%d:",x+1);
        wordSearch(words, grid, gridRow+1, gridCol);
        x++;
        freeArray(grid,gridRow+1);
    }
    freeArray(words, listlength);

}


char** getWords(int rows, int cols){

    int i;

    //allocate top level of pointers.
    char** words = malloc(sizeof(char*)*rows);

    //allocate each individual array
    for(i=0; i<rows; i++){
        words[i] = malloc(sizeof(char)*cols+1);
    }

    //read dictionary.txt
    FILE *dictionary = fopen("dictionary.txt", "r");
    for(i=0; i<rows; i++){
        fgets(words[i], cols+1,dictionary);
    }

    fclose(dictionary);
    return words;
}

char** makeGridArray(int rows, int cols){

    //allocate top level of pointers.
    char** grid = malloc(sizeof(char*)*rows);
    int i,j;

    //allocate each individual array
    for(i=0; i<rows;i++){
        grid[i] = malloc(sizeof(char)*cols+1);
    }
    //read in user input grid
    for(i=0;i<rows;i++){
        gets(grid[i]);
    }
    return grid;
}

int binsearch(char** dictionary, char** puzzle, int low, int high){

    int mid;

    if(low == 0 && high == 0){
        return 0;
    }

    mid = (low+high)/2 ;

    if(strcmp(*puzzle,dictionary[mid]) == 0){
            //found a match
        return 1;
    }

    else if(strcmp(*puzzle,dictionary[mid]) > 0){
            //check upper half
        return binsearch(dictionary,puzzle,mid+1,high);
    }

    else if(strcmp(*puzzle,dictionary[mid]) < 0){
        //check lower half
        return binsearch(dictionary,puzzle,low,mid-1);
    }
    else return 0;

}

char wordSearch(char** dictionary, char** puzzle, int row, int col){

    int i, X, Y, dir = 0;
    char* wordsfound[20]= {'[=11=]'};
    for (X=0;X<row+1;X++){
        for(Y=0;Y<col;Y++){
            for(dir=0;dir<DX_SIZE;dir++) //check every direction
                for(i=0;i<19;i++){
                    //will continue in direction DX,DY starting at x,y
                    int nextX = X + DX[dir] * i;
                    int nextY = Y + DY[dir] * i;
                    if(nextX < 0 || nextX >= row) break; //keep in bounds
                    if(nextY < 0 || nextY >= col) break;
                    //store the string of letters
                    *wordsfound[i] = (puzzle[nextX][nextY]);
                    if(i>2){ //minimum word is 3
                    //if the string of letters is actually a word, print
                        int bin = binsearch(dictionary,wordsfound,1,listlength);
                        if(bin){
                            printf("%s\n",wordsfound);
                        }
                    }
                }
        }
    }

}


void freeArray(char** array, int rows){
    //free arrays
    int i;
    for(i=0; i<rows; i++){
        free(array[i]);
    }
    free(array);
}

Answer 1

这里：

    char* wordsfound[20]= {'[=10=]'};
    for (X=0;X<row+1;X++){
        for(Y=0;Y<col;Y++){
            for(dir=0;dir<DX_SIZE;dir++) //check every direction
                for(i=0;i<19;i++){
                    ...
                    *wordsfound[i] = (puzzle[nextX][nextY]);

应该是：

    char wordsfound[20]= {'[=11=]'};                    /* not 20 pointers! */
    for (X=0;X<row+1;X++){
        for(Y=0;Y<col;Y++){
            for(dir=0;dir<DX_SIZE;dir++) //check every direction
                for(i=0;i<19;i++){
                    ...
                    wordsfound[i] = (puzzle[nextX][nextY]);   /* no '*' */
                    wordsfound[i+1] = '[=11=]';           /* end the string */

此外，在您的 binsearch 函数中，当您检查上半部分或下半部分时，您需要确保 mid+1 和 mid-1 分别仍然是数组中的有效索引。如果您访问数组边界之外的元素，坏事正等着您呢。

例如，如果 low = 0 和 high = 1：

mid = (low+high)/2 ;       /* this is zero */

所以你与数组元素 0 比较并决定你需要查看下半部分，现在你调用 low as mid-1 即 -1。哦不！

Answer 2

你有

char* wordsfound[20]= {'[=10=]'};

上面只是让20个char pointers全部指向NULL。

那么你就是在取消引用

*wordsfound[i] = (puzzle[nextX][nextY]);

所以，它崩溃了，因为 wordsfound[i] 是 NULL。

编辑： 因此，您必须更改 wordsfound 的声明。如果按照@John Hascall 和@J V A 的建议将其更改为 char wordsfound[20]，那么你需要这样做：

char wordSearch(char** dictionary, char** puzzle, int row, int col){

    int i, X, Y, dir = 0;
    char wordsfound[20]= {'[=12=]'};
    for (X=0;X<row+1;X++){
        for(Y=0;Y<col;Y++){
            for(dir=0;dir<DX_SIZE;dir++) //check every direction
                for(i=0;i<19;i++){
                    //will continue in direction DX,DY starting at x,y
                    int nextX = X + DX[dir] * i;
                    int nextY = Y + DY[dir] * i;
                    if(nextX < 0 || nextX >= row) break; //keep in bounds
                    if(nextY < 0 || nextY >= col) break;
                    //store the string of letters
                    wordsfound[i] = (puzzle[nextX][nextY]);
                    if(i>2){ //minimum word is 3
                        wordsfound[i+1]= '[=12=]'; // yes you need null char before passing to binsearch for strcmp to work.
                        //if the string of letters is actually a word, print
                        int bin = binsearch(dictionary, &wordsfound,1,listlength);
                        if(bin){
                           printf("%s\n",wordsfound);
                        }
                    }
                }

            }
        }

    }

即您需要将 &wordsfound 传递给 binsearch 因为 binsearch 将 char ** 作为第二个参数。

您可以只传递 wordsfound，但在那种情况下，将 binsearch 函数的第二个参数更改为 char * puzzle 并在 strcmp 中使用 puzzle *puzzle 在 binsearch.

内

但是，如果您的目标不是像假设的 JVA 先生那样将单个字符传递给 binsearch，那么您需要采取不同的方式。在这种情况下，您需要使用二维字符数组或指向字符数组的指针。在这种情况下，您需要更改 wordsearch 中的当前代码。如果使用pointer to a char array，则需要分配内存

尝试用 C 编写单词搜索程序

Trying to make word search program in C

c

grid

binary-search

strcmp

wordsearch