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);
}
}
}