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这个题的问题在于二分搜索后的结果的平方一定要小于目标值,所以特殊情况下要减一
class Solution {
public:
int mySqrt(int x) {
int l = 0;
int r = x;
long mid = l + ((r - l) >> 1);
while(l <= r){
mid = l + ((r - l) >> 1);
long res = mid * mid;
if(res < x){
l = mid + 1;
}else if(res > x){
r = mid - 1;
if(l > r){
mid = r;
}
}else{
break;
}
}
return mid;
}
};