A. Soldier and Bananas
題意:第一個香蕉要k 刀,第二個2 k 刀,第i 個要i ∗ k 刀。現有n 刀,問可以買幾個香蕉。
題解:等差數列求和,我們知道只需要找到p 使得∑ i = 1 p i ∗ k ≤ n < ∑ i = 1 p + 1 i ∗ k
即可,移項就可以得到公式,同時上述求和公式是單調遞增的,因此也可以二分答案。
參考代碼:
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std ;
typedef long long ll;
inline ll foo(int x, int k) {
return (((1L L + x) * x) >> 1 ) * k;
}
ll gao(ll k, ll n, ll w) {
return max(foo(w, k) - n, 0L L);
}
int main() {
int k, n, w;
while (~scanf (" %d %d %d" , &k, &n, &w)) {
printf ("%I64d\n" , gao(k, n, w));
}
return 0 ;
}
B. Soldier and Badges
題意:給n 個數,1 ≤ a i ≤ n ,將一個數從a 變大成b 需要消耗b − a 個金幣,問如何把這堆數變成兩兩不等的,順序任意。
題解:直接掃一遍,對一個數a ,向上找一個之前沒有佔用的位置填充即可。
參考代碼:
#include <cstdio>
#include <cstring>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std ;
const int MAX = 6007 ;
bool vis[MAX];
int foo(int x) {
int res = 0 ;
while (vis[x]) {
++x;
++res;
}
vis[x] = true ;
return res;
}
int main() {
int n;
while (~scanf (" %d" , &n)) {
memset (vis, false , sizeof (vis));
int a, sum = 0 ;
for (int i = 1 ; i <= n; ++i) {
scanf (" %d" , &a);
sum += foo(a);
}
printf ("%d\n" , sum);
}
return 0 ;
}
C. Soldier and Cards
題意:兩堆牌,每次取最上面的兩張比較,如果更大,則喫掉另一張,並將其放到底部,然後將自己這張也放到底部。一張牌都沒有時爲輸。問遊戲能不能終止,如果能,輸出誰勝利以及需要進行幾輪。
題解:考慮到總牌數並不多(k 1 + k 2 = n , 2 ≤ n ≤ 10 ),狀態數最多隻有A 10 10 ∗ C 1 9 這麼多,實際上要少得多,因此直接狀態壓縮模擬即可。
參考代碼:
#include <cstdio>
#include <cstring>
#include <set>
#include <map>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std ;
struct State {
vector <int > left;
vector <int > right;
bool operator ==(const State& B)const {
if (left.size() != B.left.size()
|| right.size() != B.right.size()) {
return false ;
}
for (int i = 0 ; i < left.size(); ++i) {
if (left[i] != B.left[i]
|| right[i] != B.right[i]) {
return false ;
}
}
return true ;
}
bool operator <(const State& B)const {
if (left.size() != B.left.size()) {
return left.size() < B.left.size();
}
for (int i = 0 ; i < left.size(); ++i) {
if (left[i] != B.left[i]) {
return left[i] < B.left[i];
}
}
if (right.size() != B.right.size()) {
return right.size() < B.right.size();
}
for (int i = 0 ; i < right.size(); ++i) {
if (right[i] != B.right[i]) {
return right[i] < B.right[i];
}
}
return false ;
}
void print() {
printf ("{\n\t%d" , left.size());
for (int i = 0 ; i < left.size(); ++i) {
printf (" %d" , left[i]);
}
printf ("\n\t%d" , right.size());
for (int i = 0 ; i < right.size(); ++i) {
printf (" %d" , right[i]);
}
puts ("\n}\n" );
}
};
map <State, bool > M;
pair<int , int > gao(State& thus) {
M.clear();
for (int i = 0 ; ; ++i) {
if (thus.left.empty()) {
return make_pair(2 , i);
} else if (thus.right.empty()) {
return make_pair(1 , i);
} else if (M.find(thus) != M.end()) {
return make_pair(-1 , i);
} else {
M.insert(make_pair(thus, true ));
if (thus.left[0 ] > thus.right[0 ]) {
thus.left.push_back(thus.right[0 ]);
thus.left.push_back(thus.left[0 ]);
} else {
thus.right.push_back(thus.left[0 ]);
thus.right.push_back(thus.right[0 ]);
}
thus.left.erase(thus.left.begin());
thus.right.erase(thus.right.begin());
}
}
}
int main() {
int n;
State my;
while (~scanf (" %d" , &n)) {
int m, a;
scanf (" %d" , &m);
my.left.clear();
while (m--) {
scanf (" %d" , &a);
my.left.push_back(a);
}
scanf (" %d" , &m);
my.right.clear();
while (m--) {
scanf (" %d" , &a);
my.right.push_back(a);
}
pair<int , int > res = gao(my);
if (res.first == -1 ) {
puts ("-1" );
} else {
printf ("%d %d\n" , res.second, res.first);
}
}
return 0 ;
}
D. Soldier and Number Game
using namespace std;
const int MAX = 5000007 ;
int flag[MAX] = {0} ;
int prime[MAX] = {0} ; //prime [i]: i的質因數的個數
int dp[MAX] = {0} ; // 前綴和
void init() {
int i;
for (i = 2 ; i <= MAX / i; ++i) {
if (flag[i] == 0 ) {
flag[i] = i;
prime[i] = 1 ;
//printf ("flag[%d ] = %d \n" , i, flag[i]);
//getchar ();
for (int j = i * i; j < MAX; j += i) {
if (flag[j] == 0 ) {
flag[j] = i;
//printf ("flag[%d ] = %d \n" , j, i);
//getchar ();
}
}
}
}
for (; i < MAX; ++i) {
if (flag[i] == 0 ) {
flag[i] = i;
prime[i] = 1 ;
}
}
for (i = 2 ; i < MAX; ++i) {
prime[i] = prime[i / flag[i]] + prime[flag[i]];
}
for (i = 1 ; i < MAX; ++i) {
dp[i] = dp[i - 1 ] + prime[i];
}
//for (int i = 1 ; i < 10 ; ++i) {
// printf ("prime[%d ] = %d , dp[%d ] = %d \n" , i, prime[i], i, dp[i]);
// }
}
int main() {
init();
int T, a, b;
scanf(" %d " , &T);
while (T--) {
scanf(" %d %d " , &a, &b);
printf ("%d \n" , dp[a] - dp[b]);
}
return 0 ;
}
E. Soldier and Traveling
題意:有n 個城市,m 條道路(無向),城市裏有一些士兵,問在每個士兵只能走一次的情況下,能不能把原來的各城市的士兵數( a 1 , a 2 , . . . a n ) 變成( b 1 , b 2 , . . . , b n ) 。如果能給出任一個 調整方案。
題解:網絡流。建圖時,增加源點s o u r c e ,匯點d e s t ,每個城市作爲一個點,同時拆點爲i 何i + n ,如果有道路( x , y ) ,那麼建邊x → n + y 和 y → n + x ,容量分別爲a x 和a y 。同時,源點和點i 1 ≤ i ≤ n 之間建邊,容量爲a x ;匯點和點i n + 1 ≤ i ≤ 2 ∗ n 之間建邊,容量爲b i 。得到s o u r c e 到d e s t 的最大流f l o w 後,判斷f l o w 是否等於所有點的士兵總和∑ n i = 1 a i 即可。當然,也應該要判斷∑ n i = 1 a i 和∑ n i = 1 b i 是否相等。
參考代碼:
#include <bits/stdc++.h>
using namespace std ;
const int INF = 0xfffffff ;
const int MAX = 107 << 1 ;
struct Edge {
int to;
int flow;
int cap;
int rev;
};
vector <Edge> G[MAX];
int level[MAX];
int ans[MAX][MAX];
int n, m;
int a[MAX], b[MAX];
void addEdge(int from, int to, int cap) {
G[from].push_back((struct Edge){to, 0 , cap, G[to].size()});
G[to].push_back((struct Edge){from, cap, cap, G[from].size() - 1 });
}
bool bfs(int s, int t) {
memset (level, -1 , sizeof (level));
level[s] = 0 ;
queue <int > Q;
Q.push(s);
while (!Q.empty()) {
int p = Q.front();
Q.pop();
for (vector <Edge> ::iterator it = G[p].begin(); it != G[p].end(); ++it) {
if (level[it->to] == -1 && it->flow < it->cap) {
Q.push(it->to);
level[it->to] = level[p] + 1 ;
if (it->to == t) {
return true ;
}
}
}
}
return false ;
}
int dfs(int s, int t, int flow) {
if (s == t) {
return flow;
}
int sum = 0 , tmp;
for (vector <Edge> ::iterator it = G[s].begin(); it != G[s].end(); ++it) {
if (level[it->to] == level[s] + 1 && it->flow < it->cap) {
tmp = dfs(it->to, t, min(flow, it->cap - it->flow));
it->flow += tmp;
G[it->to][it->rev].flow -= tmp;
sum += tmp;
flow -= tmp;
}
}
return sum;
}
int dinic(int s, int t) {
int sum = 0 ;
while (bfs(s, t)) {
sum += dfs(s, t, INF);
}
return sum;
}
inline int ex(int x) {
return (x >= 1 && x <= n) ? x : x - n;
}
int main() {
while (~scanf (" %d %d" , &n, &m)) {
for (int i = 0 ; i < MAX; ++i) {
G[i].clear();
}
int source = 0 , dest = n << 1 | 1 ;
int sum1 = 0 , sum2 = 0 ;
for (int i = 1 ; i <= n; ++i) {
scanf (" %d" , a + i);
sum1 += a[i];
addEdge(source, i, a[i]);
addEdge(i, i + n, a[i]);
}
for (int i = 1 ; i <= n; ++i) {
scanf (" %d" , b + i);
sum2 += b[i];
addEdge(i + n, dest, b[i]);
}
int x, y;
for (int i = 1 ; i <= m; ++i) {
scanf (" %d %d" , &x, &y);
addEdge(x, n + y, a[x]);
addEdge(y, n + x, a[y]);
}
int flow = dinic(source, dest);
if (sum1 != sum2 || flow != sum2) {
puts ("NO" );
} else {
puts ("YES" );
memset (ans, 0 , sizeof (ans));
for (int i = 1 ; i <= n; ++i) {
ans[i][i] = a[i];
}
for (int i = 1 ; i <= n; ++i) {
for (int j = 0 ; j < G[i].size(); ++j) {
Edge& e = G[i][j];
if (e.flow > 0 ) {
ans[i][i] -= e.flow;
ans[i][e.to - n] += e.flow;
}
}
}
for (int i = 1 ; i <= n; ++i) {
for (int j = 1 ; j <= n; ++j) {
printf ("%d%c" , ans[i][j], j == n ? '\n' : ' ' );
}
}
}
}
return 0 ;
}