'commit'

TangDou/AcWing/BinarySearch/ZhengTiErFen/POJ2104_Prepare.cpp

@@ -0,0 +1,60 @@
+#include <iostream>
+#include <algorithm>
+#include <cstring>
+using namespace std;
+const int N = 1025;
+
+//快读
+int read() {
+    int x = 0, f = 1;
+    char ch = getchar();
+    while (ch < '0' || ch > '9') {
+        if (ch == '-') f = -1;
+        ch = getchar();
+    }
+    while (ch >= '0' && ch <= '9') {
+        x = (x << 3) + (x << 1) + (ch ^ 48);
+        ch = getchar();
+    }
+    return x * f;
+}
+
+//树状数组
+int tr[N];
+void add(int x, int c) {
+    for (; x < N; x += x & -x) tr[x] += c;
+}
+//查询x的个数和
+int getSum(int x) {
+    int sum = 0;
+    for (; x; x -= x & -x) sum += tr[x];
+    return sum;
+}
+
+//从1开始查找第k小的数
+int getKth(int k) {
+    int l = 1, r = N - 1; //保证数组不能越界
+    while (l < r) {
+        int mid = (l + r) >> 1;
+        if (getSum(mid) >= k)
+            r = mid;
+        else
+            l = mid + 1;
+    }
+    return l;
+}
+/*
+测试用用例:
+2 9 1 3 12 7 6 -1
+3
+
+答案：
+3
+*/
+int main() {
+    int x;
+    while (x = read(), ~x) add(x, 1); // x这个位置上+1
+    int k = read();
+    printf("%d\n", getKth(k));
+    return 0;
+}