【kmp】Corporate Identity HDU

来源：互联网发布：汉朝知乎编辑：程序博客网时间：2024/06/05 15:35

Think:
1知识点：kmp算法+暴力枚举
2题意：输入一组字符串，寻找最长公共子串，长度相同时选择字典序最小的
3解题思路：
（1）：找到字符串组中长度最短的字符串，然后根据左右区间枚举查询
（2）：找到字符串组中长度最短的字符串，然后根据长度从大至小枚举，若在当前长度梯度已经找到串，则结束枚举（因为从大至小枚举的长度梯度级，因此下面枚举的长度梯度级要小于当前已经枚举完成的长度梯度级）
4反思：
（1）：len数组记录的是字符串组数，定义时应大于临界字符串组数(4000)，定义时定义的是至少大于临界最长字符串长度(200)，导致数组越界
（2）：字符串数组’\0’位置，混淆变量导致放置位置错误

vjudge题目链接

以下为Wrong Answer代码——字符串数组’\0’位置，混淆变量导致放置位置错误

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int inf = 0x3f3f3f3f;const int max_size = 244;int _next[max_size], len[max_size];char st[4014][max_size], st1[max_size], st2[max_size], st3[max_size];void get_next(char *P, int len_P);bool kmp(char *T, int len_T, char *P, int len_P);int main(){    int n, i, j, k, tmp, t;    while(~scanf("%d", &n) && n){        tmp = inf;        for(i = 0; i < n; i++){            scanf("%s", st[i]);            len[i] = strlen(st[i]);            if(len[i] < tmp){                tmp = len[i], t = i;            }        }        strcpy(st1, st[t]);        int ans = 0;        for(i = 0; i < tmp; i++){            for(j = i; j < tmp; j++){                if(j-i+1 < ans) continue;                t = 0;                for(k = i; k <= j; k++){                    st2[t++] = st1[k];                }                st2[k] = '\0';                for(k = 0; k < n; k++){                    if(!kmp(st[k], len[k], st2, j-i+1)){                        break;                    }                }                if(k < n)                    continue;                if(j-i+1 > ans){                    strcpy(st3, st2);                    ans = j-i+1;                }                else {                    if(strcmp(st2, st3) < 0){                        strcpy(st3, st2);                        ans = j-i+1;                    }                }            }        }        if(ans) printf("%s\n", st3);        else printf("IDENTITY LOST\n");    }    return 0;}void get_next(char *P, int len_P){    int q, k;    _next[0] = 0;    k = 0;    for(q = 1; q < len_P; q++){        while(k > 0 && P[q] != P[k]){            k = _next[k-1];        }        if(P[q] == P[k])            k++;        _next[q] = k;    }    return;}bool kmp(char *T, int len_T, char *P, int len_P){    int k, i;    get_next(P, len_P);    k = 0;    for(i = 0; i < len_T; i++){        while(k > 0 && P[k] != T[i]){            k = _next[k-1];        }        if(P[k] == T[i])            k++;        if(k == len_P) return true;    }    return false;}

以下为Wrong Answer代码——数组越界-提示Wrong Answer错误-why???

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int inf = 0x3f3f3f3f;const int max_size = 244;int _next[max_size], len[max_size];char st[4014][max_size], st1[max_size], st2[max_size], st3[max_size];void get_next(char *P, int len_P);bool kmp(char *T, int len_T, char *P, int len_P);int main(){    int n, i, j, k, tmp, t;    while(~scanf("%d", &n) && n){        tmp = inf;        for(i = 0; i < n; i++){            scanf("%s", st[i]);            len[i] = strlen(st[i]);            if(len[i] < tmp){                tmp = len[i], t = i;            }        }        strcpy(st1, st[t]);        int ans = 0;        for(i = 0; i < tmp; i++){            for(j = i; j < tmp; j++){                if(j-i+1 < ans) continue;                t = 0;                for(k = i; k <= j; k++){                    st2[t++] = st1[k];                }                st2[t] = '\0';                for(k = 0; k < n; k++){                    if(!kmp(st[k], len[k], st2, j-i+1))                        break;                }                if(k != n)                    continue;                if(j-i+1 > ans || !ans){                    strcpy(st3, st2);                    ans = j-i+1;                }                else {                    if(strcmp(st2, st3) < 0){                        strcpy(st3, st2);                        ans = j-i+1;                    }                }            }        }        if(ans) printf("%s\n", st3);        else printf("IDENTITY LOST\n");    }    return 0;}void get_next(char *P, int len_P){    int q, k;    _next[0] = 0;    k = 0;    for(q = 1; q < len_P; q++){        while(k > 0 && P[q] != P[k]){            k = _next[k-1];        }        if(P[q] == P[k])            k++;        _next[q] = k;    }    return;}bool kmp(char *T, int len_T, char *P, int len_P){    int k, i;    get_next(P, len_P);    k = 0;    for(i = 0; i < len_T; i++){        while(k > 0 && P[k] != T[i]){            k = _next[k-1];        }        if(P[k] == T[i])            k++;        if(k == len_P) return true;    }    return false;}

以下为Accepted代码——解题思路（1）

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int inf = 0x3f3f3f3f;const int max_size = 244;int _next[max_size], len[4014];char st[4014][max_size], st1[max_size], st2[max_size], st3[max_size];void get_next(char *P, int len_P);bool kmp(char *T, int len_T, char *P, int len_P);int main(){    int n, i, j, k, tmp, t;    while(~scanf("%d", &n) && n){        tmp = inf;        for(i = 0; i < n; i++){            scanf("%s", st[i]);            len[i] = strlen(st[i]);            if(len[i] < tmp){                tmp = len[i], t = i;            }        }        strcpy(st1, st[t]);        int ans = 0;        for(i = 0; i < tmp; i++){            for(j = i; j < tmp; j++){                if(j-i+1 < ans) continue;                t = 0;                for(k = i; k <= j; k++){                    st2[t++] = st1[k];                }                st2[t] = '\0';                for(k = 0; k < n; k++){                    if(!kmp(st[k], len[k], st2, j-i+1))                        break;                }                if(k != n)                    continue;                if(j-i+1 > ans || !ans){                    strcpy(st3, st2);                    ans = j-i+1;                }                else {                    if(strcmp(st2, st3) < 0){                        strcpy(st3, st2);                        ans = j-i+1;                    }                }            }        }        if(ans) printf("%s\n", st3);        else printf("IDENTITY LOST\n");    }    return 0;}void get_next(char *P, int len_P){    int q, k;    _next[0] = 0;    k = 0;    for(q = 1; q < len_P; q++){        while(k > 0 && P[q] != P[k]){            k = _next[k-1];        }        if(P[q] == P[k])            k++;        _next[q] = k;    }    return;}bool kmp(char *T, int len_T, char *P, int len_P){    int k, i;    get_next(P, len_P);    k = 0;    for(i = 0; i < len_T; i++){        while(k > 0 && P[k] != T[i]){            k = _next[k-1];        }        if(P[k] == T[i])            k++;        if(k == len_P) return true;    }    return false;}

以下为Accepted代码——解题思路（2）

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int inf = 0x3f3f3f3f;const int max_size = 204;int _next[max_size], len[4014];char st[4004][max_size], st1[max_size], ans[max_size];void get_next(char *P, int len_P);bool kmp(char *T, int len_T, char *P, int len_P);int main(){    int n, i, j, k, len1, id;    while(~scanf("%d", &n) && n){        id = 0, len1 = inf;        for(i = 0; i < n; i++){            scanf("%s", st[i]);            len[i] = strlen(st[i]);            if(len[i] < len1){                len1 = len[i], id = i;            }        }        bool flag = false;        for(i = len1; i >= 1 && !flag; i--){            for(j = 0; j+i <= len1; j++){                for(k = 0; k < i; k++){                    st1[k] = st[id][k+j];                }                st1[i] = '\0';                get_next(st1, i);                for(k = 0; k < n; k++){                    int len_T = strlen(st[k]);                    if(kmp(st[k], len_T, st1, i) == false)                        break;                }                if(k == n){                    if(!flag){                        strcpy(ans, st1);                        flag = true;                    }                    else if(flag && strcmp(st1, ans) < 0){                        strcpy(ans, st1);                    }                }            }        }        if(flag) puts(ans);        else puts("IDENTITY LOST");    }    return 0;}void get_next(char *P, int len_P){    int q, k;    _next[0] = 0;    k = 0;    for(q = 1; q < len_P; q++){        while(k > 0 && P[q] != P[k]){            k = _next[k-1];        }        if(P[q] == P[k])            k++;        _next[q] = k;    }    return;}bool kmp(char *T, int len_T, char *P, int len_P){    int k, i;    k = 0;    for(i = 0; i < len_T; i++){        while(k > 0 && P[k] != T[i]){            k = _next[k-1];        }        if(P[k] == T[i])            k++;        if(k == len_P) return true;    }    return false;}

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