46 lines
923 B
Rust
46 lines
923 B
Rust
/**
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* [2552] Count Increasing Quadruplets
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*/
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pub struct Solution {}
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// submission codes start here
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impl Solution {
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pub fn count_quadruplets(nums: Vec<i32>) -> i64 {
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let nums: Vec<usize> = nums.iter().map(|x| *x as usize).collect();
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let n = nums.len();
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let mut pre = vec![0; n + 1];
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let mut result = 0;
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for j in 0..n {
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let mut suffix = 0;
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for k in (j + 1..n).rev() {
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if nums[j] > nums[k] {
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result += pre[nums[k]] * suffix;
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} else {
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suffix += 1;
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}
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}
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for i in nums[j] + 1..=n {
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pre[i] += 1;
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}
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}
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result
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}
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}
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// submission codes end
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_2552() {
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assert_eq!(2, Solution::count_quadruplets(vec![1, 3, 2, 4, 5]));
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}
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}
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