## 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.

## Rust Solution

``````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];
btm.insert(l, i);
}
for i in 0..n {
let r = intervals[i];
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);
}
``````

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