题解 | 平方根

#include <stdio.h>

//二分f法

int main(void) {

int n;

if (scanf("%d", &n) != 1) return 0;

long long L = 0, R = (long long)n + 1; // 开区间 (L, R)

while (L + 1 < R) {

long long mid = (L + R) >> 1;

if (mid * mid <= n) L = mid;

else R = mid;

}

printf("%lld\n", L);

return 0;

}