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FirstBadVersion.java
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46 lines (40 loc) · 1.65 KB
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// You are a product manager and currently leading a team to develop a new product.
// Unfortunately, the latest version of your product fails the quality check.
// Since each version is developed based on the previous version, all the versions after
// a bad version are also bad.
// Suppose you have n versions [1, 2, ..., n] and you want to find out the first bad one,
// which causes all the following ones to be bad.
// You are given an API bool isBadVersion(version) which will return whether version is bad.
// Implement a function to find the first bad version.
// You should minimize the number of calls to the API.
// See: https://leetcode.com/problems/first-bad-version/
package leetcode.binary_search;
public class FirstBadVersion {
public int firstBadVersion(int n) {
return (int) binarySearch(1, n);
}
/**
* We need to use long instead int here because l + r can exceed the maximum int
* value
*/
private long binarySearch(long l, long r) {
if (l > r)
return l;
// Here is the trap (l + r) > Integer.MAX_VALUE is possible
// Another approach is to use:
// int mid = l + (r - l)/2
long mid = (l + r) / 2;
if (isBadVersion((int) mid))
return binarySearch(l, mid - 1);
else
return binarySearch(mid + 1, r);
}
// The isBadVersion API is defined in the parent class VersionControl.
boolean isBadVersion(int version) {
return version >= 1702766719;
}
public static void main(String[] args) {
FirstBadVersion sln = new FirstBadVersion();
System.out.println(sln.firstBadVersion(2126753390));
}
}