c - 尝试用C语言编写单词搜索程序

Question

给定从文件中读取的用于所有测试用例的输入字典和几个单词搜索网格，我想识别字典中出现在每个单词搜索网格中的所有单词。

我已经阅读了dictionary.txt文件，并且我相信它可以读取任何字母网格，但我在尝试查找dictionary.txt文件中出现的网格中的单词时遇到了困难。我决定对各个方向的字符串使用递归二分搜索，但这对我来说有点复杂。

我的程序一直运行，直到到达单词搜索功能，它尝试在网格中查找单词，然后它会崩溃，但我不知道为什么，也不确定我是否走在正确的轨道上。

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]= {'\0'};
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);
                    }
                }
            }
    }
}

}

但这是我的整个代码

#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]= {'\0'};
    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]= {'\0'};
    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]= {'\0'};                    /* 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] = '\0';           /* end the string */

另外，在你的binsearch函数中，当你去检查上半部分或下半部分时，你需要确保分别是mid+1和mid-1仍然是数组的有效索引。如果您访问数组边界之外的元素，就会有不好的事情等着您。

例如，如果low = 0且high = 1:

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

因此，您与数组元素 0 进行比较，并决定需要查看下半部分，现在您使用 low 作为 mid-1 进行调用，即 -1。哦不!