436. Find Right Interval

You are given an array of intervals, where intervals[i] = [starti, endi] and each starti is unique.

The right interval for an interval i is an interval j such that startj >= endi and startj is minimized.

Return an array of right interval indices for each interval i. If no right interval exists for interval i, then put -1 at index i.

Example 1:

Input: intervals = [[1,2]]
Output: [-1]
Explanation: There is only one interval in the collection, so it outputs -1.

Example 2:

Input: intervals = [[3,4],[2,3],[1,2]]
Output: [-1,0,1]
Explanation: There is no right interval for [3,4].
The right interval for [2,3] is [3,4] since start0 = 3 is the smallest start that is >= end1 = 3.
The right interval for [1,2] is [2,3] since start1 = 2 is the smallest start that is >= end2 = 2.

Example 3:

Input: intervals = [[1,4],[2,3],[3,4]]
Output: [-1,2,-1]
Explanation: There is no right interval for [1,4] and [3,4].
The right interval for [2,3] is [3,4] since start2 = 3 is the smallest start that is >= end1 = 3.

Constraints:

• 1 <= intervals.length <= 2 * 104
• intervals[i].length == 2
• -106 <= starti <= endi <= 106
• The start point of each interval is unique.

436. Find Right Interval
struct Solution;
use std::collections::BTreeMap;

impl Solution {
fn find_right_interval(intervals: Vec<Vec<i32>>) -> Vec<i32> {
let n = intervals.len();
let mut res: Vec<i32> = vec![-1; n];
let mut btm: BTreeMap<i32, usize> = BTreeMap::new();
for i in 0..n {
let l = intervals[i][0];
btm.insert(l, i);
}
for i in 0..n {
let r = intervals[i][1];
for (_, &j) in btm.range(r..).take(1) {
res[i] = j as i32;
}
}
res
}
}

#[test]
fn test() {
let intervals = vec_vec_i32![[1, 2]];
let res = vec![-1];
assert_eq!(Solution::find_right_interval(intervals), res);
let intervals = vec_vec_i32![[3, 4], [2, 3], [1, 2]];
let res = vec![-1, 0, 1];
assert_eq!(Solution::find_right_interval(intervals), res);
let intervals = vec_vec_i32![[1, 4], [2, 3], [3, 4]];
let res = vec![-1, 2, -1];
assert_eq!(Solution::find_right_interval(intervals), res);
}