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fix counting liars #4141

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merged 5 commits into from
Dec 28, 2023
Merged

fix counting liars #4141

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68edefc
fix counting liars
SansPapyrus683 Dec 28, 2023
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[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Dec 28, 2023
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Apply suggestions from code review
SansPapyrus683 Dec 28, 2023
bff437e
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Dec 28, 2023
73b3448
Update usaco-1228.mdx
SansPapyrus683 Dec 28, 2023
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76 changes: 34 additions & 42 deletions solutions/bronze/usaco-1228.mdx
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Original file line number Diff line number Diff line change
Expand Up @@ -41,16 +41,14 @@ int main() {

sort(cows.begin(), cows.end());

/*
* lying_left[i] stores the number of cows to the left of cow i
* that must be lying given that Bessie is at the position of cow i.
*/
// lying_left[i] stores the number of cows to the left of cow i
// that must be lying given that Bessie is at the position of cow i.
vector<int> lying_left(n);
for (int i = 1; i < n; i++) {
// Add up all the cows that are already lying to the left of our pos.
// Add up all the cows that are lying to the left of our pos.
lying_left[i] += lying_left[i - 1];

if (cows[i - 1].second == 'L' && cows[i].first > cows[i - 1].first) {
if (cows[i - 1].second == 'L' && cows[i].first >= cows[i - 1].first) {
/*
* If the cow before says our position is to the left
* but their position is strictly less than our position,
Expand All @@ -60,16 +58,14 @@ int main() {
}
}

/*
* lying_right stores the same thing, but does it so for the cows
* to the *right* of i.
*/
// lying_right stores the same thing, but does it so for the cows
// to the *right* of i.
vector<int> lying_right(n);
// Fill it up in much the same way.
for (int i = n - 2; i >= 0; i--) {
lying_right[i] += lying_right[i + 1];

if (cows[i + 1].second == 'G' && cows[i].first < cows[i + 1].first) {
if (cows[i + 1].second == 'G' && cows[i].first <= cows[i + 1].first) {
lying_right[i]++;
}
}
Expand All @@ -92,14 +88,20 @@ import java.util.*;

public class CountingLiars {
// BeginCodeSnip{Cow Class}
static class Cow {
static class Cow implements Comparable<Cow> {
char statement;
int pos;

public Cow(char statement, int pos) {
this.statement = statement;
this.pos = pos;
}

@Override
public int compareTo(Cow c) {
if (pos != c.pos) { return pos - c.pos; }
return statement - c.statement;
}
}
// EndCodeSnip

Expand All @@ -116,19 +118,17 @@ public class CountingLiars {
}
read.close();

Arrays.sort(cows, Comparator.comparingInt(c -> c.pos));
Arrays.sort(cows);

/*
* lying_left[i] stores the number of cows to the left of cow i
* that must be lying given that Bessie is at the position of cow i.
*/
// lying_left[i] stores the number of cows to the left of cow i
// that must be lying given that Bessie is at the position of cow i.
int[] lying_left = new int[n];
for (int i = 1; i < n; i++) {
// Add up all the cows that are already lying to the left of our
// pos.
// Add up all the cows that are lying to the left of our pos.
lying_left[i] += lying_left[i - 1];

if (cows[i - 1].statement == 'L' && cows[i].pos > cows[i - 1].pos) {
if (cows[i - 1].statement == 'L' &&
cows[i].pos >= cows[i - 1].pos) {
/*
* If the cow before says our position is to the left
* but their position is strictly less than our position,
Expand All @@ -138,16 +138,15 @@ public class CountingLiars {
}
}

/*
* lying_right stores the same thing, but does it so for the cows
* to the *right* of i.
*/
// lying_right stores the same thing, but does it so for the cows
// to the *right* of i.
int[] lying_right = new int[n];
// Fill it up in much the same way.
for (int i = n - 2; i >= 0; i--) {
lying_right[i] += lying_right[i + 1];

if (cows[i + 1].statement == 'G' && cows[i].pos < cows[i + 1].pos) {
if (cows[i + 1].statement == 'G' &&
cows[i].pos <= cows[i + 1].pos) {
lying_right[i]++;
}
}
Expand Down Expand Up @@ -180,35 +179,28 @@ for _ in range(n):
statement, pos = input().split()
cows.append(Cow(int(pos), statement))

cows.sort(key=lambda c: c.pos)
cows.sort(key=lambda c: (c.pos, c.statement))

"""
lying_left[i] stores the number of cows to the left of cow i
that must be lying given that Bessie is at the position of cow i.
"""
# lying_left[i] stores the number of cows to the left of cow i
# that must be lying given that Bessie is at the position of cow i.
lying_left = [0 for _ in range(n)]
for i in range(1, n):
# Add up all the cows that are already lying to the left of our pos.
# Add up all the cows that are lying to the left of our pos.
lying_left[i] += lying_left[i - 1]

if cows[i - 1].statement == "L" and cows[i].pos > cows[i - 1].pos:
"""
If the cow before says our position is to the left
but their position is strictly less than our position,
they're lying.
"""
if cows[i - 1].statement == "L" and cows[i].pos >= cows[i - 1].pos:
# If the cow before says our position is to the left
# but their position is strictly less than our position, they're lying.
lying_left[i] += 1

"""
lying_right stores the same thing, but does it so for the cows
to the *right* of i.
"""
# lying_right stores the same thing, but does it so for the cows
# to the *right* of i.
lying_right = [0 for _ in range(n)]
# Fill it up in much the same way.
for i in range(n - 2, -1, -1):
lying_right[i] += lying_right[i + 1]

if cows[i + 1].statement == "G" and cows[i].pos < cows[i + 1].pos:
if cows[i + 1].statement == "G" and cows[i].pos <= cows[i + 1].pos:
lying_right[i] += 1

min_liars = n
Expand Down