HDU 6343 Problem L. Graph Theory Homework (思維)
There is a complete graph containing n vertices, the weight of the i-th vertex is wi.
The length of edge between vertex i and j (i≠j) is .
Calculate the length of the shortest path from 1 to n
.
Input
The first line of the input contains an integer T
(1≤T≤10)
denoting the number of test cases.
Each test case starts with an integer n (1≤n≤105) denoting the number of vertices in the graph.
The second line contains n integers, the i-th integer denotes wi (1≤wi≤105)
.
Output
For each test case, print an integer denoting the length of the shortest path from 1
to n
.
Sample Input
1
3
1 3 5
Sample Output
2
從前一個點可以任意選擇下一個點, 每個點有一個權值, 點和點之間的距離是,權值差的絕對值開根號再向下取整,求從1 到n最短距離。
剛開始做這個題, 覺得是個水題, (實際上確實是個水題),寫了個 n ^ 2的記憶化搜尋, 抱著僥倖心理交了一次, 不出意外的超時了~
實際上我們可以假設有某中間點k, 使得直接從1到n的路線鬆弛, 那麼有
兩邊平方就會發現, k的存在是矛盾的,所以知道最短距離是從1直接到n。
AC程式碼:
#include<cstdio> #include<iostream> #include<cmath> using namespace std; int main() { int i, j, T, ans, n, q, m; int s[100005]; scanf("%d", &T); while(T--){ scanf("%d", &n); for(i = 1;i <= n;i++) scanf("%d", &a); m = abs(s[1] - s[n]); ans = (int)sqrt(m * 1.0); printf("%d\n", ans); } return 0; }