过河问题，需要dp吗？每次能跳到的最远的地方，这样就能保证，跳跃次数最少了。感觉可以，但只过60%. import java.io.*; import java.util.*; public class Main { public static void main(String[] args) { Scanner in = new Scanner(System.in); while (in.hasNext()) { int n = Integer.valueOf(in.nextLine()); String s = in.nextLine(); if (n == 0) { System.out.println(-1); continue; } String[] ss = s.split("\\s"); int[] a = new int[ss.length]; for (int i = 0; i < a.length; i++) { a[i] = Integer.valueOf(ss[i]); } int count = 1; int i = 0; for (; i < a.length;) { int step = a[i]; if (a[i] == 0) { System.out.println(-1); break; } if (i + a[i] >= a.length) { System.out.println(count); break; } int j = i + a[i]; for (; j > i && a[j] == 0; j--) { } if (j == i) { System.out.println(-1); break; } else { i = j; count++; } } } } }