洛谷 P1120 小木棍［数据加强版］

最新推荐文章于 2024-02-25 16:48:57 发布

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博主分享了在解决洛谷P1120小木棍问题时遇到的数据加强版挑战，遇到了意料之外的TLE问题，对原有解法进行了探讨。

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开始被一个不知到是什么鬼的小地方弄得TLE了,也是很难受

之前是这么写的

#include <algorithm>
#include <iostream>
#include <vector>
#include <cstdio>
using namespace std;

const int maxn = 65+10, inf = 0x3f3f3f3f;
int s[maxn], m[maxn], Max = - inf, Min = inf, sum;
bool isget, yinzi[maxn*maxn];
vector<int> s_;

bool cmp ( int a, int b ) { return a < b; }

void dfs( int exlength, int last, int cur, int pos ) {
    //printf("%d %d %d %d\n", exlength, last, cur, pos);
    if( last == 0 ) {
        printf("%d\n", exlength);
        exit(0);
    }
    if( cur == exlength ) {
        dfs( exlength, last-1, 0, 0 );
        return;
    }
    for( int j = pos; j <= s_.size(); j++ ) {
        int i = s_[j];
        if( !s[i] ) continue;
        if( i + cur > exlength ) break; //
        s[i]--; //使用这根棍子
        dfs( exlength, last, cur+i, j );
        s[i]++;
        if( cur == 0 || cur + i == exlength ) return;
    }
}

int main() {
    int n, temp;
    scanf("%d", &n);
    while(n--) {
        scanf("%d", &temp);
        if( temp > 50 ) continue;
        s_.push_back(temp);
        s[temp]++;
        m[temp]++;
        sum += temp;
        Max = Max < temp ? temp : Max;
        Min = Min > temp ? temp : Min;
    }
    sort(s_.begin(), s_.end(), cmp);
    for( int i = Max; ; i++ ) {
        if( sum % i ) continue;
        bool go = false;
        dfs( i, sum / i - 1, 0, 0 );
    }
    return 0;
}

后来改成下面这样居然神奇的AC了,黑人问号???

#include <algorithm>
#include <iostream>
#include <vector>
#include <cstdio>
#include <ctime>
using namespace std;

const int maxn = 65+10, inf = 0x3f3f3f3f;
int s[maxn], m[maxn], Max = - inf, Min = inf, sum;
clock_t b;

void dfs( int exlength, int last, int cur, int pos ) {
    //printf("%d %d %d %d\n", exlength, last, cur, pos);
    if( last == 0 ) {
        printf("%d\n", exlength);
        //printf("cost: %dms\n", clock()-b);
        exit(0);
    }
    if( cur == exlength ) {
        dfs( exlength, last-1, 0, Max );
        return;
    }    for( int i = pos; i >= Min; i-- ) {        if( s[i] && i + cur <= exlength ) {
            s[i]--; //使用这根棍子
            dfs( exlength, last, cur+i, i );
            s[i]++;
            if( cur == 0 || cur + i == exlength ) return;
        }
    }
    return;
}

int main() {
    int n, temp;
    scanf("%d", &n);
    while(n--) {
        scanf("%d", &temp);
        if( temp > 50 ) continue;
        s[temp]++;
        m[temp]++;
        sum += temp;
        Max = Max < temp ? temp : Max;
        Min = Min > temp ? temp : Min;
    }
    b = clock();
    for( int i = Max; ; i++ ) {
        if( sum % i ) continue;
        dfs( i, sum / i - 1, 0, Max );
    }
    return 0;
}