sgu 154 二分 + 数学方法 sgu 111 二分 + 高精度 （Java）

/*
 * sgu154.c
 *
 *  Created on: 2011-10-1
 *      Author: bjfuwangzhu
 */

#include<stdio.h>
#define nnum 5
#define nmax 0x7fffffff
int getNum(int n) {
    int res;
    res = 0;
    while (n) {
        res += n / nnum;
        n /= nnum;
    }
    return res;
}
void solve(int n) {
    int left, right, mid, temp;
    left = 0, right = nmax;
    while (left <= right) {
        mid = (left + right) >> 1;
        temp = getNum(mid);
        if (temp >= n) {
            right = mid - 1;
        } else {
            left = mid + 1;
        }
    }
    if (getNum(left) == n) {
        printf("%d\n", left);
        return;
    }
    puts("No solution");
}
int main() {
#ifndef ONLINE_JUDGE
    freopen("data.in", "r", stdin);
#endif
    int n;
    while (~scanf("%d", &n)) {
        if (n == 0) {
            puts("1");
            continue;
        }
        solve(n);
    }
    return 0;
}

import java.io.BufferedInputStream;
import java.math.BigInteger;
import java.util.Scanner;

public class Solution {
    public static void main(String[] args) {
        Scanner cin = new Scanner(new BufferedInputStream(System.in));
        BigInteger num, left, right, mid, two = BigInteger.valueOf(2), one = BigInteger.ONE;
        while (cin.hasNext()) {
            num = cin.nextBigInteger();
            left = BigInteger.ZERO;
            right = num.abs().add(one);
            while (left.compareTo(right) <= 0) {
                mid = left.add(right).divide(two);
                if (mid.multiply(mid).compareTo(num) >= 0) {
                    right = mid.subtract(one);
                } else {
                    left = mid.add(one);
                }
            }
            while (left.multiply(left).compareTo(num) > 0) {
                left = left.subtract(one);
            }
            System.out.println(left);
        }
    }
}