[Description] Given two different strings, find the largest successive common substring.
e.g. str1[]="qwertyuiopasdfgh"; str2[]="jhdfgqwertyudfxcv";
LCsubstr[]="qwertyu";
[Thought] show the correspondence result of this two strings from the 2-D array of 'record[][]', and find the longest non-zero diagonal elements. To save the auxiliary space, we can use only 1-D array 'record[]' to implement. O(n^2) O(m)
[Implementation] C code:
1 #include<stdio.h> 2 #include<stdlib.h> 3 #include<string.h> 4 5 char* LCS(char longer[], char shorter[]) 6 { 7 int longer_len=strlen(longer); 8 int shorter_len=strlen(shorter); 9 int record[shorter_len]; 10 int i,j,max_len=0,substr_end=0,substr_begin; 11 12 for(i=0;i<longer_len;i++) 13 { 14 for(j=shorter_len-1;j>=0;j--) 15 { 16 if(longer[i]==shorter[j]) 17 { 18 if(0==i || 0==j) 19 { 20 record[j]=1; 21 } 22 else 23 { 24 record[j]=record[j-1]+1; 25 } 26 } 27 else 28 { 29 record[j]=0; 30 } 31 32 if(record[j]>max_len) 33 { 34 max_len=record[j]; 35 substr_end=j; 36 } 37 } 38 } 39 40 substr_begin=substr_end-max_len+1; 41 42 // char substr[max_len]; 43 char* substr=(char*)malloc(max_len); 44 for(i=0;i<max_len;i++) 45 { 46 substr[i]=shorter[substr_begin+i]; 47 } 48 return substr; 49 } 50 51 int main() 52 { 53 char longer[]="asdfghjklqwertyyuio"; 54 char shorter[]="zxvsdffghwerxv"; 55 56 printf("The longer str:\n\t%s\n",longer); 57 printf("The shorter str:\n\t%s\n",shorter); 58 printf("The lagest common str:\n\t%s\n",LCS(longer,shorter)); 59 return 0; 60 }
