最长回文字串理解（学习Manacher's algorithm）

#include <string.h>
#include <stdio.h>
#include <iostream>
using namespace std;
void preprocess(char str[],char result[]);
int min(int a, int b);
int p[2020];
int main(){
    int center,i,i_,L,R,j;
    char str[1010],result[2020];
    int maxlen, index,len;
    cin.getline(str,1000,‘\n‘);
    preprocess(str,result);
    /*printf("%s",result);*/
    //handle the string
    center=0,R=0;
    p[0]=0;
    len = strlen(result);
    //i from 1,so the begging position is placed ‘$‘ to avoid the segment error
    for(i=1;i<len-1;i++){
        i_=center*2-i;//the symmetric position
        L=center*2-R;
        p[i] = (R > i) ? min(R - i, p[i_]) : 0;
        while (i + p[i] + 1<len&&result[i + p[i] + 1] == result[ i- p[i] - 1])
            p[i]++;
        //if R expands,then modify it
        if (R - i <p[i]){
            center = i;
            R = i + p[i];
        }
    }
    //find the maximum length in p
    maxlen = 0, index = 0;
    for (i = 0; i < strlen(result); i++){
        if (maxlen < p[i]){
            maxlen = p[i];
            index = i;
        }
    }
    printf("%d", maxlen);
    return 0;
}
void preprocess(char str[],char result[]){
    int len=strlen(str),i,j;
    result[0]=‘$‘;//indicates the start 
    for(i=0,j=1;i<len;i++){
        result[j++]=‘#‘;
        result[j++]=str[i];
    }
    result[j]=‘#‘;
    result[j+1]=‘\0‘;
}
int min(int a, int b){
    if (a < b)
        return a;
    else
        return b;
}