From f10403c366aad1f6721670cb75e12e152488780b Mon Sep 17 00:00:00 2001
From: Ankit Singh <ankitsinankitsin888000@gmail.com>
Date: Fri, 2 Jul 2021 15:01:53 +0530
Subject: [PATCH] solution using pairs

---
 src/1087 - Shortest Subsequence.cpp | 113 ++++++++++++++++++----------
 1 file changed, 72 insertions(+), 41 deletions(-)

diff --git a/src/1087 - Shortest Subsequence.cpp b/src/1087 - Shortest Subsequence.cpp
index adb6623..4dd88c5 100644
--- a/src/1087 - Shortest Subsequence.cpp	
+++ b/src/1087 - Shortest Subsequence.cpp	
@@ -1,46 +1,77 @@
 /*
-Problem Name: Shortest Subsequence
-Problem Link: https://cses.fi/problemset/task/1087
-Author: Sachin Srivastava (mrsac7)
+
 */
+
+
 #include<bits/stdc++.h>
 using namespace std;
 
-// #define int long long
-#define endl '\n'
-
-signed main(){
-    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
-    #ifdef LOCAL
-    freopen("input.txt", "r" , stdin);
-    freopen("output.txt", "w", stdout);
-    #endif
-    
-    string s; cin>>s;
-    int l = 0, r = 0;
-    bool a = 0, b = 0, c = 0, d = 0;
-    int n = s.size();
-    string ans;
-    while(l < n) {
-        a = 0, b = 0, c = 0, d = 0;
-        a += (s[l] == 'A'); b += (s[l] == 'C');
-        c += (s[l] == 'G'); d += (s[l] == 'T');
-        r = l+1;
-        while(r < n && a+b+c+d != 4) {
-            a += (s[r] == 'A'); b += (s[r] == 'C');
-            c += (s[r] == 'G'); d += (s[r] == 'T');
-            r++;
-        }
-        if (a+b+c+d == 4)
-            ans += s[r-1];
-        l = r;
-    }
-    cerr<<a<<' '<<b<<' '<<c<<' '<<d;
-    if (a+b+c+d == 4)
-        ans += 'A';
-    else if (!a) ans += 'A';
-    else if (!b) ans += 'C';
-    else if (!c) ans += 'G';
-    else if (!d) ans += 'T';
-    cout<<ans;
-}
\ No newline at end of file
+#define fastio ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL)
+#define int long long int
+#define sz(a) (int)a.size()
+#define ff first
+#define ss second
+#define inf 1e18
+#define pb push_back
+#define eb emplace_back
+#define vi vector<int>
+#define mod 1000000007
+#define pi pair<int, int>
+#define ti tuple<int, int, int>
+#define all(v) (v).begin(),(v).end()
+#define allr(v) (v).rbegin(), (v).rend()
+#define set_bits(x) __builtin_popcountll(x)
+#define deb(x) cout << "[" << #x << " = " << x << "]"
+#define deb2(x, y) cout << "[" << #x << " = " << x << "  " << #y << " = " << y << "]"
+#define output_vector(a) for(auto x : a) cout << x << " "
+#define output_vector2(a) for(auto i : a) { for(auto j : i) cout << j << " "; cout << "\n"; }
+
+void solve() {
+	string s;
+	cin >> s;
+	
+	int n = sz(s);
+	
+	pi g = {0, 0}, c = {0, 0}, a = {0, 0}, t = {0, 0};
+	
+	int k = 0;
+	string ans;
+	for(int i = 0; i < n; i++) {
+		if(s[i] == 'G') g.ff++, g.ss = i;
+		else if(s[i] == 'C') c.ff++, c.ss = i;
+		else if(s[i] == 'A') a.ff++, a.ss = i;
+		else if(s[i] == 'T') t.ff++, t.ss = i;
+		if(g.ff && c.ff && a.ff && t.ff) {
+			k++;
+//			deb(i);
+			int j = max({g.ss, c.ss, a.ss, t.ss});
+			ans += s[j]; 
+			g = c = a = t = {0, 0};
+		}
+	}
+	
+	
+	if(a.ff == 0) ans += "A";
+	else if(c.ff == 0) ans += "C";
+	else if(g.ff == 0) ans += "G";
+	else if(t.ff == 0) ans += "T";
+	else ans += "A";
+	cout << ans << "\n";
+}
+
+int32_t main() {
+
+	fastio;
+
+	int test_cases = 1;
+//	cin >> test_cases;
+
+	while(test_cases--) {
+	   solve();
+	}
+	
+	cerr << "Time elapsed : " << 1.0 * clock() / CLOCKS_PER_SEC << " sec \n ";
+
+	return 0;
+}
+