【HDOJ】3183 A Magic Lamp

RMQ。

/* 3183 */
#include <cstdio>
#include <cstring>
#include <cstdlib>

#define MAXN 1005

char s[MAXN], ans[MAXN];
int dp[MAXN][MAXN];
int n,len,m;

int min(int x, int y) {
    return s[x]<=s[y] ? x:y;
}

void RMQ_init() {
    int i, j, k;

    for (i=1; i<=len; ++i)
        dp[i][0] = i;
    for (j=1; (1<<j)<=len; ++j)
        for (i=1; i+(1<<j)-1<=len; ++i)
            dp[i][j] = min(dp[i][j-1], dp[i+(1<<(j-1))][j-1]);
}

int RMQ(int l, int r) {
    int k = 0;

    while ((1<<(k+1)) <= r-l+1)
        ++k;
    return min(dp[l][k], dp[r-(1<<k)+1][k]);
}

int main() {
    int i, j, k;
    int l;

    #ifndef ONLINE_JUDGE
        freopen("data.in", "r", stdin);
        freopen("data.out", "w", stdout);
    #endif

    while (scanf("%s %d", s+1, &m)!=EOF) {
        len = strlen(s+1);
        RMQ_init();
        m = len - m;
        l = k = 1;
        while (m--) {
            k = RMQ(k, len-m);
            ans[l++] = s[k++];
        }
        for (i=1; i<l; ++i)
            if (ans[i] != '0')
                break;
        ans[l] = '';
        if (i == l)
            puts("0");
        else
            puts(ans+i);
    }

    return 0;
}