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367_Valid_Perfect_Square.java

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class Solution {

/* public boolean isPerfectSquare(int num) {

int i = 1;

while (num > 0) {

num -= i;

i += 2;

}

return num == 0;

} */

public boolean isPerfectSquare(int num) {

int low = 1;

int high = num;

while (low <= high) {

long mid = (low + high) >>> 1;

if (mid * mid == num) {

return true;

} else if (mid * mid < num) {

low = (int) mid + 1;

} else {

high = (int) mid - 1;

}

}

return false;

}

/* public boolean isPerfectSquare(int num) {

long x = num;

while (x * x > num) {

x = (x + num / x) >> 1;

}

return x * x == num;

} */

}