AtCoder Regular Contest #002

111th.

論理演算子を逆に書かなかったり, 0初期化の変数を１で初期化しなかったり, ちゃんと貪欲法を書かないと僕みたいにA~Cでそれぞれ１つずつWAしてしまいます.
こういうの気をつけないと...
A.

#include <stdio.h>

int main(void)
{
    int y;
    
    scanf("%d", &y);
    
    if (y % 4 == 0 && (y % 100 != 0 || y % 400 == 0)){
        printf("YES\n");
    }
    else {
        printf("NO\n");
    }
    
    return (0);
}

B.

#include <stdio.h>

int canDivide(int y, int m, int d)
{
    if (y % m == 0){
        y /= m;
        if (y % d == 0){
            return (1);
        }
    }
    return (0);
}

int isLeap(int y)
{
    return (y % 4 == 0 && (y % 100 != 0 || y % 400 == 0));
}

int main(void)
{
    int y, m, d, flag;
    int table[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    
    scanf("%d/%d/%d", &y, &m, &d);
    
    while (canDivide(y, m, d) == 0){
        flag = 0;
        if (isLeap(y) && m == 2){
            flag = 1;
        }
        if (table[m - 1] + flag > d){
            d++;
        }
        else if (table[m - 1] + flag == d){
            m++;
            d = 1;
            if (m == 13){
                m = 1;
                y++;
            }
        }
    }
    
    printf("%d/%02d/%02d\n", y, m, d);
    
    return (0);
}

C.

#include <stdio.h>
#include <string.h>

int min(int a, int b)
{
    return (b > a ? a : b);
}

int simulate(char *str, char *L, char *R)
{
    int i;
    int ret;
    
    i = 0;
    ret = 0;
    while (str[i] != '\0'){
        if (str[i + 1] == '\0'){
            return (++ret);
        }
        if (strncmp(&str[i], L, 2) == 0 || strncmp(&str[i], R, 2) == 0){
            ret++;
            i += 2;
        }
        else {
            ret++;
            i++;
        }
    }
    return (ret);
}

int main(void)
{
    char cmd[16][4] = {"AA", "BB", "XX", "YY", "AB", "BA", "AX", "XA", "AY", "YA", "BX", "XB", "BY", "YB", "XY", "YX"};
    char L[4], R[4];
    int n, ans;
    int i, j;
    char button[1024];
    
    scanf("%d", &n);
    ans = n;
    scanf("%s", button);
    
    for (i = 0; i < 16; i++){
        for (j = 0; j < 16; j++){
            strcpy(L, cmd[i]);
            strcpy(R, cmd[j]);
            ans = min(ans, simulate(button, L, R));
        }
    }
    
    printf("%d\n", ans);
    
    return (0);
}