Created
August 19, 2014 13:09
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CodeIQ「中学入試から:数列の和」解答コード
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#include <stdio.h> | |
typedef unsigned long long ull; | |
typedef struct { | |
ull syoko, kosa; | |
} sequence_info_t; | |
/* seq_strを読み取り、整数でsequenceに格納する。その要素数を返す。 */ | |
unsigned read_sequence(const char *seq_str,ull sequence[]) { | |
ull current_value=0; | |
int read_num=0; | |
for (;;) { | |
if(*seq_str == ',' || *seq_str == '\0') { | |
sequence[read_num++] = current_value; | |
current_value = 0; | |
if (*seq_str == '\0') break; | |
} else { | |
current_value = current_value * 10 + *seq_str - '0'; | |
} | |
seq_str++; | |
} | |
return read_num; | |
} | |
/* 数列の第index項の値を得る */ | |
ull get_sequence_value(int si_num,const sequence_info_t si[], int index) { | |
return si[index % si_num].syoko + si[index % si_num].kosa * (index / si_num); | |
} | |
/* 非負整数を文字列に変換する */ | |
void ull_to_str(char *out, ull num) { | |
char buffer[64]; | |
char *p = buffer; | |
do { | |
*(p++) = (num % 10) + '0'; | |
} while ((num /= 10) > 0); | |
do { | |
*(out++) = *(--p); | |
} while (p != buffer); | |
*out = '\0'; | |
} | |
/* 二つの文字列が同一かを判定する(同一なら非0、同一でないなら0を返す) */ | |
int is_same_strings(const char *s1, const char *s2) { | |
while (*s1 != '\0' || *s2 != '\0') { | |
if (*(s1++) != *(s2++)) return 0; | |
} | |
return 1; | |
} | |
int main(void) { | |
char id[32]; | |
char seq_str[1024]; | |
int b, c; | |
char expected_answer[64]; | |
while (scanf("%s%s%d%d%s", id, seq_str, &b, &c, expected_answer) == 5) { | |
char real_answer[64]; | |
ull sequence[1000]; | |
int seq_length; | |
sequence_info_t si[1000]; | |
int si_num; | |
int i; | |
int accepted = 0; | |
seq_length = read_sequence(seq_str, sequence); | |
/* 問題の数列は複数の等差数列を混ぜたものと推測し、 | |
* 等差数列の数とそれぞれの初項および公差を求める */ | |
for (si_num = 1; si_num <= seq_length / 2; si_num++) { | |
/* 初項と公差を求める */ | |
for (i = 0; i < si_num; i++) { | |
si[i].syoko = sequence[i]; | |
si[i].kosa = sequence[i + si_num] - sequence[i]; | |
} | |
/* 数列と合っているか確かめる */ | |
accepted = 1; | |
for (i = 0; i < seq_length; i++) { | |
if (get_sequence_value(si_num, si, i) != sequence[i]) { | |
accepted = 0; | |
break; | |
} | |
} | |
if (accepted) break; | |
} | |
if (accepted) { | |
/* 数列の生成規則が見つかった */ | |
ull sum = 0; | |
for ( i = b - 1; i < c; i++) { | |
/* 愚直に和を求める */ | |
sum += get_sequence_value(si_num, si, i); | |
} | |
/* 和を文字列に変換する */ | |
ull_to_str(real_answer, sum); | |
/* 答えが一致するかを確かめる */ | |
if (!is_same_strings(expected_answer, real_answer)) { | |
fprintf(stderr, "%s,", id); | |
printf("%s : expected %s, got %s\n", id, expected_answer, real_answer); | |
} | |
} else { | |
printf("%s : ERROR unsupported sequence\n", id); | |
continue; | |
} | |
} | |
putc('\n', stderr); | |
return 0; | |
} |
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