【CAIOJ 1178】 最长共同前缀长度

【题目链接】

            点击打开链接

【算法】

          EXKMP

【代码】

             

#include<bits/stdc++.h>
using namespace std;
#define MAXL 1000010

int i,N,l1,l2;
char s1[MAXL],s2[MAXL];
int extend[MAXL],next[MAXL];

template <typename T> inline void read(T &x) {
        int f = 1; x = 0;
        char c = getchar();
        for (; !isdigit(c); c = getchar()) { if (c == '-') f = -f; }
        for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - '0';
        x *= f;
}
template <typename T> inline void write(T x) {
    if (x < 0) { putchar('-'); x = -x; }
    if (x > 9) write(x/10);
    putchar(x%10+'0');
}
template <typename T> inline void writeln(T x) {
    write(x);
    puts("");
}
inline void getnext() {
        int i=0,pos,j;
        next[0] = l2;
        while (s2[i] == s2[i+1] && i + 1 < l2) i++;
        next[1] = i;
        pos = 1;
        for (i = 2; i < l2; i++) {
                if (i + next[i-pos] < pos + next[pos]) next[i] = next[i-pos];
                else {
                        j = pos + next[pos] - i;
                        if (j < 0) j = 0;
                        while (i + j < l2 && s2[j] == s2[i+j]) j++;
                        next[i] = j;
                        pos = i;
                }        
        }        
}

inline void exkmp() {
        int i=0,pos,j;
        while (s1[i] == s2[i] && i < l1 && i < l2) i++;
        extend[0] = i;
        pos = 0;
        for (i = 1; i < l1; i++) {
                if (i + next[i-pos] < pos + extend[pos]) extend[i] = next[i-pos];
                else {
                        j = pos + extend[pos] - i;
                        if (j < 0) j = 0;
                        while (i + j < l1 && j < l2 && s1[i+j] == s2[j]) j++;
                        extend[i] = j;
                        pos = i;
                }         
        }
}

int main() {
        
        scanf("%s",&s1);
        scanf("%s",&s2);
        l1 = strlen(s1); l2 = strlen(s2);
        
        getnext();
        exkmp();
        
        for (i = 0; i < l1; i++) {
                if (!i) write(extend[i]);
                else {
                        putchar(' ');
                        write(extend[i]);
                }
        }
        
        puts("");
        
        return 0;
    
}