51Nod－1010－只包含2 3 5的数

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ACM模版

描述

题解

先打表生成丑数，然后二分查找到大于等于n的第一个数。

代码

#include <iostream>#include <cstdio>#include <queue>using namespace std;typedef unsigned long long ull;const int MAXN = 1e4 + 1e3;/* * Ugly Numbers * Ugly numbers are numbers whose only prime factors are 2, 3 or 5. * 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, ... */typedef pair<ull, int> node_type;ull result[MAXN];void init(){    priority_queue<node_type, vector<node_type>, greater<node_type>> Q;    Q.push(make_pair(1, 2));    for (int i = 0; i < MAXN; i++)    {        node_type node = Q.top();        Q.pop();        switch (node.second)        {            case 2:                Q.push(make_pair(node.first * 2, 2));            case 3:                Q.push(make_pair(node.first * 3, 3));            case 5:                Q.push(make_pair(node.first * 5, 5));        }        result[i] = node.first;    }    return ;}/* *  传入参数必须l <= h *  假设a数组已经按从小到大排序 *  返回值l总是合理的 */int bs(ull a[], int l, int h, ull v){    int m;    while (l < h)    {        m = (l + h) >> 1;        if (a[m] < v)        {            l = m + 1;        }        else        {            h = m;        }    }    return l;}int main(int argc, const char * argv[]){    freopen("input.txt", "r", stdin);//    freopen("input.txt", "w", stdin);    init();    int T;    cin >> T;    ull n;    while (T--)    {        cin >> n;        int key = bs(result, 1, MAXN - 1, n);        cout << result[key] << '\n';    }    return 0;}

参考

STL简介
二分查找

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