Solve problems 072A, 072B, 072C and 072D from atcoder

Author: AliOsm

AtCoder/072A - Sandglass2.cpp

@@ -0,0 +1,15 @@
+#include <stdio.h>
+ 
+using namespace std;
+
+int main() {
+	int x, t;
+	scanf("%d %d", &x, &t);
+ 
+	if(t <= x)
+		printf("%d\n", x - t);
+	else
+		puts("0");
+ 
+    return 0;
+}

AtCoder/072B - OddString.cpp

@@ -0,0 +1,15 @@
+#include <iostream>
+#include <string>
+ 
+using namespace std;
+
+int main() {
+	string s;
+	cin >> s;
+	for(int i = 0; i < s.length(); ++i)
+		if(i % 2 == 0)
+			cout << s[i];
+	cout << endl;
+ 
+    return 0;
+}

AtCoder/072C - Together.cpp

@@ -0,0 +1,25 @@
+#include <stdio.h>
+#include <algorithm>
+ 
+using namespace std;
+
+int const N = 1e5 + 5;
+int n, fr[N];
+
+int main() {
+	scanf("%d", &n);
+	for(int i = 0, tmp; i < n; ++i) {
+		scanf("%d", &tmp);
+		++fr[tmp];
+	}
+ 
+	int res = fr[0] + fr[1];
+	for(int i = 1; i < N - 1; ++i) {
+		res = max(res, fr[i] + fr[i - 1] + fr[i + 1]);
+	}
+	res = max(res, fr[N] + fr[N - 1]);
+ 
+	printf("%d\n", res);
+ 
+    return 0;
+}

AtCoder/072D - Derangement.cpp

@@ -0,0 +1,36 @@
+#include <stdio.h>
+ 
+using namespace std;
+
+int const N = 1e5 + 5;
+int n, a[N];
+ 
+int main() {
+	scanf("%d", &n);
+	for(int i = 1; i <= n; ++i)
+		scanf("%d", a + i);
+ 
+	int res = 0;
+ 
+	if(a[1] == 1) {
+		swap(a[1], a[2]);
+		++res;
+	}
+ 
+	for(int i = 2; i < n; ++i) {
+		if(a[i] == i) {
+			swap(a[i], a[i + 1]);
+			--i;
+			++res;
+		}
+	}
+ 
+	if(a[n] == n) {
+		swap(a[n], a[n - 1]);
+		++res;
+	}
+ 
+	printf("%d\n", res);
+ 
+    return 0;
+}

AtCoder/README.md

@@ -14,3 +14,7 @@
 - [060D - Simple Knapsack](http://abc060.contest.atcoder.jp/tasks/arc073_b)
 - [014A - Cookie Exchanges](http://agc014.contest.atcoder.jp/tasks/agc014_a)
 - [014B - Unplanned Queries](http://agc014.contest.atcoder.jp/tasks/agc014_b)
+- [072A - Sandglass2](http://abc072.contest.atcoder.jp/tasks/abc072_a)
+- [072B - OddString](http://abc072.contest.atcoder.jp/tasks/abc072_b)
+- [072C - Together](http://abc072.contest.atcoder.jp/tasks/arc082_a)
+- [072D - Derangement](http://abc072.contest.atcoder.jp/tasks/arc082_b)