ACM Same binary weight

Same binary weight

时间限制：300 ms  |  内存限制：65535 KB

难度：3

 

描述

The binary weight of a positive  integer is the number of 1's in its binary representation.for example,the decmial number 1 has a binary weight of 1,and the decimal number 1717 (which is 11010110101 in binary) has a binary weight of 7.Give a positive integer N,return the smallest integer greater than N that has the same binary weight as N.N will be between 1 and 1000000000,inclusive,the result is guaranteed to fit in a signed 32-bit interget.

 

输入

The input has multicases and each case contains a integer N.

输出

For each case,output the smallest integer greater than N that has the same binary weight as N.

样例输入

1717
4
7
12
555555

样例输出

1718
8
11
17
555557
解题思路  1. 将右起第一个“01”，改变为“10”  2. 将该“01”后面的所有“1”移动至最后

#include <iostream>
#include <string>
#include <bitset>
#include <algorithm>
using namespace std;

int main(){
    int n;
    while(cin >> n){
        bitset<32> bitInt(n);
        string strInt =bitInt.to_string();
        int pos = strInt.rfind("01");
        swap(strInt[pos],strInt[pos+1]);
        if(pos+2 < 31) sort(strInt.begin()+pos+2,strInt.end());
        cout<<bitset<32>(strInt).to_ulong()<<endl;
    }
}

 string rfind("01")从字符串右边找”01“然后返回”01“的位置

将01后面的1移动到最后相当于对01后面的字符串排序