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FindRightInterval.java
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FindRightInterval.java
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package src.java.medium.map;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;
public class FindRightInterval {
// TreeMap
public int[] findRightInterval(int[][] intervals) {
TreeMap<Integer, Integer> map = new TreeMap<>();
int len = intervals.length;
int[] ret = new int[len];
for (int i=0; i<len; i++)
map.put(intervals[i][0], i);
for (int i=0; i<len; i++) {
Map.Entry<Integer, Integer> entry = map.ceilingEntry(intervals[i][1]);
if (entry == null) ret[i] = -1;
else ret[i] = entry.getValue();
}
return ret;
}
// Binary search solution
public int[] findRightInterval2(int[][] intervals) {
Map<Integer, Integer> startToIndex = new HashMap<>();
int len = intervals.length;
int[] ret = new int[len];
int[] starts = new int[len];
for (int i=0; i<len; i++) {
starts[i] = intervals[i][0];
startToIndex.put(intervals[i][0], i);
}
Arrays.sort(starts);
for (int i=0; i<len; i++) {
int s = binarySearch(starts, intervals[i][1]);
if (s == -1) ret[i] = -1;
else ret[i] = startToIndex.get(s);
}
return ret;
}
private int binarySearch(int[] nums, int t) {
int lo = 0, hi = nums.length-1;
int mid = -1;
while(lo <= hi) {
mid = lo + (hi - lo)/2;
if (nums[mid] == t) return nums[mid];
else if (nums[mid] < t) lo = mid+1;
else {
if (mid > 0 && nums[mid-1] < t)
return nums[mid];
else
hi = mid-1;
}
}
return -1;
}
}