Solve problems 779A, 779B, 779C and 779D from codeforces

Author: AliOsm

CodeForces/779A. Pupils Redistribution.cpp

@@ -0,0 +1,35 @@
+#include <stdio.h>
+#include <algorithm>
+
+using namespace std;
+
+int const N = 6;
+int n, a[N], b[N];
+
+int main() {
+	scanf("%d", &n);
+	for(int i = 0, tmp; i < n; ++i) {
+		scanf("%d", &tmp);
+		++a[tmp];
+	}
+	for(int i = 0, tmp; i < n; ++i) {
+		scanf("%d", &tmp);
+		++b[tmp];
+	}
+
+	int res = 0;
+	for(int i = 1; i <= 5; ++i) {
+		if((a[i] + b[i]) % 2 != 0) {
+			puts("-1");
+			return 0;
+		}
+
+		int tmp = (a[i] + b[i]) >> 1;
+		tmp = max(a[i], b[i]) - tmp;
+		res += tmp;
+	}
+
+	printf("%d\n", res / 2);
+
+    return 0;
+}

CodeForces/779B. Weird Rounding.cpp

@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <string.h>
+
+using namespace std;
+
+int k;
+char s[11];
+
+int main() {
+	scanf("%s %d", s, &k);
+
+	int len = strlen(s);
+	int res = 0, del = 0;
+	for(int i = len - 1; i >= 0; --i) {
+		if(s[i] == '0')
+			++res;
+		else
+			++del;
+		if(res == k)
+			break;
+	}
+
+	if(res == k)
+		printf("%d\n", del);
+	else
+		printf("%d\n", len - 1);
+
+    return 0;
+}

CodeForces/779C. Dishonest Sellers.cpp

@@ -0,0 +1,40 @@
+#include <stdio.h>
+#include <algorithm>
+
+using namespace std;
+
+int const N = 2e5 + 1;
+int n, k;
+
+struct node {
+	int b, a, d;
+
+	bool operator<(const node &n) const {
+		return d < n.d;
+	}
+};
+
+node a[N];
+
+int main() {
+	scanf("%d %d", &n, &k);
+	for(int i = 0; i < n; ++i)
+		scanf("%d", &a[i].b);
+	for(int i = 0; i < n; ++i) {
+		scanf("%d", &a[i].a);
+		a[i].d = a[i].b - a[i].a;
+	}
+	sort(a, a + n);
+
+	int res = 0, i = 0;
+	for(; i < k; ++i)
+		res += a[i].b;
+	for(; i < n && a[i].d <= 0; ++i)
+		res += a[i].b;
+	for(; i < n; ++i)
+		res += a[i].a;
+
+	printf("%d\n", res);
+
+    return 0;
+}

CodeForces/779D. String Game.cpp

@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <vector>
+#include <algorithm>
+#include <string.h>
+
+using namespace std;
+
+int const N = 2e5 + 1;
+int n, m, a[N];
+char s[N], p[N];
+vector<pair<int, char> > tmp;
+
+bool can(int mid) {
+	tmp.clear();
+
+	for(int i = mid; i < n; ++i)
+		tmp.push_back(make_pair(a[i], s[a[i]]));
+	sort(tmp.begin(), tmp.end());
+
+	for(int i = 0, j = 0; i < m; ++i) {
+		while(j < (int)tmp.size() && tmp[j].second != p[i])
+			++j;
+
+		if(j == (int)tmp.size())
+			return false;
+
+		++j;
+	}
+
+	return true;
+}
+
+int main() {
+	scanf("%s %s", s, p);
+	n = strlen(s);
+	m = strlen(p);
+	for(int i = 0; i < n; ++i) {
+		scanf("%d", a + i);
+		--a[i];
+	}
+
+	int l = 0, r = n, mid, res = 0;
+	while(l <= r) {
+		mid = (l + r) / 2;
+		if(can(mid)) {
+			l = mid + 1;
+			res = mid;
+		} else
+			r = mid - 1;
+	}
+
+	printf("%d\n", res);
+
+    return 0;
+}

CodeForces/README.md

@@ -201,6 +201,10 @@
 - [757A. Gotta Catch Em' All!](http://codeforces.com/contest/757/problem/A)
 - [766A. Mahmoud and Longest Uncommon Subsequence](http://codeforces.com/contest/766/problem/A)
 - [766D. Mahmoud and a Dictionary](http://codeforces.com/contest/766/problem/D)
+- [779A. Pupils Redistribution](http://codeforces.com/contest/779/problem/A)
+- [779B. Weird Rounding](http://codeforces.com/contest/779/problem/B)
+- [779C. Dishonest Sellers](http://codeforces.com/contest/779/problem/C)
+- [779D. String Game](http://codeforces.com/contest/779/problem/D)
 - [780A. Andryusha and Socks](http://codeforces.com/problemset/problem/780/A)
 - [785A. Anton and Polyhedrons](http://codeforces.com/contest/785/problem/A)
 - [785B. Anton and Classes](http://codeforces.com/contest/785/problem/B)